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Endocrinology Vol. 138, No. 11 4792-4797
Copyright © 1997 by The Endocrine Society

ARTICLES

Maternal Adrenalectomy Eliminates a Surge of Plasma Dehydroepiandrosterone in the Mother and Attenuates the Prenatal Testosterone Surge in the Male Fetus1

Partha Sinha, Ildiko Halasz, Jennifer F. Choi, Robert F. McGivern and Eva Redei

Departments of Pharmacology and Psychiatry (P.S., I.H., J.F.C., E.R.), University of Pennsylvania, Philadelphia, Pennsylvania 19104; and Department of Psychology (R.F.M.), San Diego State University, San Diego, California 92120

Address all correspondence and requests for reprints to: Eva Redei, Ph.D., The Asher Center, Department of Psychiatry and Behavioral Sciences, Northwestern University Medical School, 303 East Chicago Avenue, Ward Building 9–142, Chicago, Illinois 60611. E-mail: e-redei{at}nwu.edu


   Abstract
Top
 Abstract
Introduction
 Materials and Methods
 Results
 Discussion
 References
 
Previous work has established a number of sex-related deficits in immune function, behavior, and endocrine responses to stress in the offspring of dams exposed to ethanol. To examine the potential role of maternal glucocorticoids as a mediator of these sexually dimorphic effects in the fetus, we examined the influence of prenatal alcohol exposure in the presence or absence of maternal glucocorticoids on fetal plasma corticosterone (CORT) production. An additional question to be addressed by these studies was whether maternal adrenalectomy could eliminate the known inhibition by ethanol of the prenatal surge of plasma testosterone in male fetuses.

Pregnant dams were adrenalectomized (ADX) or sham-adrenalectomized on gestational day (G) 7 and placed on a liquid diet containing 35% ethanol-derived calories or pair-fed an isocaloric control diet throughout the experiment. On G18, G19, and G21, plasma levels of CORT, testosterone, and dehydroepiandrosterone (DHEA) were measured in male and female fetuses and their mothers. Ethanol administration consistently increased maternal plasma CORT levels but did not significantly alter CORT levels in the fetus. Maternal ADX resulted in compensatory increases in fetal CORT levels that were lower in fetuses of ADX dams on alcohol, suggesting a direct effect of ethanol on fetal pituitary-adrenal activity. There were no significant sex differences in fetal plasma CORT levels in response to any of these manipulations.

A novel surge of maternal plasma DHEA was found on G19 that was absent in plasma from ADX dams. In spite of the absence of a surge on G19, plasma DHEA levels of ADX dams rose from very low levels at G18 to levels on G21 that were significantly higher than in Sham dams. A normal testosterone surge was observed in male fetuses on G18 and G19 from sham-adrenalectomized dams administered the pair-fed diet. However, this surge was greatly attenuated in males administered ethanol and also in male fetuses from ADX dams. These results reveal a direct inhibitory influence of ethanol on fetal CORT secretion as well as on the prenatal testosterone surge in males. Furthermore, these studies demonstrate the presence of a surge of DHEA in the pregnant rat. Overall, these data suggest that there is a critical adrenal factor in the rat that regulates the maternal surge of DHEA on G19 and the prenatal testosterone surge of male fetuses on G18–19.


   Introduction
Top
 Abstract
 Introduction
Materials and Methods
 Results
 Discussion
 References
 
EXPOSURE TO alcohol during early development has been associated with altered behavior, endocrine functions, and immune deficits in humans and in experimental animals (1, 2, 3). Many of these alcohol-related deficits exhibit a sex difference that may be associated with incomplete neurobehavioral sexual differentiation of the male offspring (4). The normal male pattern of these measures is organizationally dependent on adequate perinatal levels of testosterone (T). A prenatal and a postnatal T surge occurs in humans and in many other mammals, including rats (5, 6, 7, 8). In the rat, prenatal ethanol exposure markedly attenuates the normal prenatal surge of T on gestational day (G)18–19 (9, 10), as well as the postnatal T surge at birth (11).

With respect to immune function, fetal alcohol exposed (FAE) male offspring exhibit impaired T cell function, an effect not observed in FAE females (12). This sexually dimorphic effect of prenatal ethanol exposure on T cell function is independent of adult sex steroid levels (13), suggesting that ethanol selectively disturbs an early organizational event in the FAE male fetus. One such developmental event may be ethanol-induced suppression of the prenatal T surge in males.

We have found that adrenalectomy of alcohol-consuming dams eliminates the immunosuppression in male offspring, but induces it in female offspring (13). These results suggest the potential involvement of a maternal adrenal factor that interacts differentially with the developing male and female immune system, leading to the developmental vulnerability of males. The most likely candidates are glucocorticoids, since their levels are increased in the mother by alcohol consumption (10, 14), and several lymphokines developmentally regulated in the thymus are known to be regulated by glucocorticoids (15, 16).

Sex differences in steroid modulation of the immune system by elevated levels of glucocorticoids and other adrenal and gonadal steroids are well established (17), and long-term effects on immune function have been observed following alterations in the early sex steroid milieu (18). Changes in glucocorticoid levels in the fetus may interact with testosterone or other androgens to produce the male-specific vulnerability of the thymic development in FAE males. Since ethanol suppresses perinatal T production, it seems unlikely that this alone can account for the sex-specific immunosuppression in adult FAE males. For this reason, we considered whether elevated maternal glucocorticoids might be an additional factor.

The other steroid possibly involved in the FAE-induced changes in fetal physiology is dehydroepiandrosterone (DHEA), an adrenal androgen in humans that is responsive to stimulation by ACTH (19). In rodents, DHEA is present in low levels peripherally (20), and both the adult (21) and fetal (22) rat adrenal were thought to lack the enzyme 17{alpha}-hydroxylase responsible for the synthesis of DHEA. However, in vitro studies suggest that the rat adrenal can produce DHEA in response to ACTH stimulation (23). If DHEA of adrenal origin exists in the pregnant rat, it may, either directly or through conversion to other steroids, interact with glucocorticoids to affect immune system development.

In this study, we examined the influence of maternal glucocorticoids on fetal corticosterone (CORT) and T production during late gestation in the presence and absence of ethanol exposure. Of particular interest to us was the question of whether maternal adrenalectomy could reverse the ethanol-induced suppression of the prenatal T surge in FAE males or whether it might influence the production of maternal DHEA. In addition, we examined the possibility that maternal adrenalectomy induces differential CORT production in male and female fetuses, an effect that might help to explain the opposite effects of maternal adrenalectomy on FAE-induced immunosuppression in male and female offspring.


   Materials and Methods
Top
 Abstract
 Introduction
 Materials and Methods
Results
 Discussion
 References
 
Animals, diets, and feeding
Female Sprague-Dawley rats (viral free, 56–68 days of age; Harlan, Indianapolis, IN) were nightly paired with male rats. On the following morning, females were separated and vaginal smears were taken. A vaginal smear positive for sperm signified the day as the first day of gestation. Pregnant dams were maintained on regular care until gestation day 7 (G7). On this day, one half of the rats underwent adrenalectomy (ADX), performed dorsally under Nembutal anesthesia (35 mg/kg). The other half were sham-adrenalectomized (Sham), meaning that they underwent surgery without the removal of adrenals. Starting on G8, all ADX and non-ADX dams were assigned to one of two experimental groups: 1) Alcohol (FAE) liquid ethanol diet ad libitum or 2) Pair-fed (PF) isocaloric liquid control diet without ethanol, equal in volume to that ingested by dams in the ethanol group.

Liquid diets were prepared by Bio-Serv, Inc. (Frenchtown, NJ) and were formulated to provide adequate nutrition to pregnant females regardless of ethanol intake. The ethanol diet contained 5% (wt/vol) ethanol and provided 35% ethanol-derived calories; maltose-dextrin was isocalorically substituted for ethanol in the liquid control diet. Fresh diet was presented daily between 1600–1700 h. ADX dams received the diet in 0.9% saline instead of water. To prevent resorption of the fetus that occurs in ADX animals after surgery (our personal observation), a very low dose of CORT (2 µg/liter) was included in the diet for 3 days after surgery. The liquid diets were continued from day 8 until day 21. Alcohol consumption of both the Sham and the ADX dams were similar to those measured previously (13).

Dams (n = 5–6/group/day) were killed on G18, 19, and 21, and the uterine horn was removed and placed on ice. Maternal trunk blood was collected for determination of plasma CORT, DHEA, and T by RIA. The sex of each fetus was determined by the anogenital distance or by microscopic examination of the gonads. After decapitation of the fetuses, trunk blood was collected in heparinized capillary tubes for measurement of fetal CORT and T. For the CORT RIA, pooling of fetal samples is not necessary, since less than 1 µl of plasma is required. For measurement of T, however, plasma from same-sex fetuses from the same litter was pooled.

All procedures were approved by the University of Pennsylvania Animals Care and Use Committee.

RIAs
Maternal blood was collected into a chilled tube containing EDTA (1.5 mg/ml whole blood), kept on ice, spun down in a refrigerated centrifuge for 20 min at 1000 x g, separated, and frozen (-70 C) in aliquots within 1 h of collection. For fetal blood collection, heparinized capillaries were used.

CORT
CORT concentrations were measured as described previously (10) in unextracted plasma, using an [125I]CORT RIA (ICN Biomedicals, Carson, CA). CORT antiserum cross-reactivity is less than 0.3% with other steroids. The assay sensitivity is 3 ng/ml, and intra- and interassay coefficients of variation were 4.7% and 7.5%, respectively.

DHEA
Serum DHEA levels were determined by a direct 125I-RIA kit (Diagnostic System Laboratories, Webster, TX) using anti-DHEA-coated tubes. Cross-reactivity of the polyclonal antibody was less than 1% to any other steroid. Assay sensitivity was 0.02 ng/ml, and intraassay coefficient of variation was 5.8%. All samples were run in one assay.

Testosterone
T was measured in unextracted plasma using an ImmuChem-coated tube [125I]testosterone RIA (ICN Biomedicals, Carson, CA). Cross-reactivity of the antibody was 7.8% for 5-dihydrotestosterone; other steroids were less than 5%. Assay sensitivity was 0.2 ng/ml; intra- and interassay coefficients of variation were 9.2% and 11.5%, respectively.

Statistical analyses
Data were analyzed using an adrenalectomy (ADX, Sham) x diet (FAE, PF) x gestational age (G18, G19, G21) ANOVA (Microsoft Systat for Windows, SYSTAT Inc., Evanston, IL). Sex was included as an additional factor where noted. Separate two-way ANOVAs (ADX or diet x gestational age) were conducted when justified by main effects in the overall analysis. Post hoc comparisons were made by Tukey multiple comparisons, with a probability of P < 0.05 considered statistically significant.


   Results
Top
 Abstract
 Introduction
 Materials and Methods
 Results
Discussion
 References
 
Maternal-fetal CORT levels
Ethanol diet and adrenalectomy markedly influenced plasma CORT levels of pregnant rats on G18, G19, and G21 (Fig. 1Go). The analysis of maternal CORT levels revealed significant main effects for ADX (F(1,44) = 79.45; P < 0.001), diet (F(1,44) = 13.93; P < 0.001), and gestational age (F(2,44) = 5.65; P < 0.01).



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  		Figure 1. Plasma CORT levels in pregnant dams during the late period of gestation (Sham/PF, sham-ADX dams on pair-fed diet; Sham/FAE, sham-ADX alcohol diet-consuming dams; ADX/PF, ADX dams on pair-fed diet; ADX/FAE, ADX alcohol diet-consuming dams). Diet for the ADX dams was prepared in 0.9% NaCl instead of water. Blood was collected between 1000–1200 h. Values are the mean ± SEM of four to five dams per group. *, P < 0.05; **, P < 0.01 comparison between diet groups; {dagger}, P < 0.05; {ddagger}, P < 0.01 comparison between ADX and Sham groups.

 
In Sham/PF dams, maternal plasma CORT levels dropped significantly on G19 compared with G18 and G21 (P < 0.01). In contrast to this fluctuation, ethanol consumption produced a consistent elevation of plasma CORT levels in dams with intact adrenals; plasma CORT levels were significantly higher on all days compared with all other groups (P < 0.05). As shown in Fig. 1Go, maternal ADX on G7 resulted in the expected low levels of maternal CORT on G18 and G19, with a small and nonsignificant rise on G21. As expected, the alcohol diet did not cause any difference in the CORT levels of the ADX dams.

Fetal plasma CORT levels, shown in Fig. 2Go, were significantly elevated by maternal ADX (ADX: F[1,463] = 105.46; P < 0.001) and decreased by maternal alcohol consumption (diet: F[2,463] = 20.45; P < 0.001). Significant main effects were also found for gestational day (F[2,463] = 24.45; P < 0.001), and significant interactions were observed between ADX x diet (F[1,463] = 15.93; P < 0.001), ADX x gestational day (F[2,463] = 46.55; P < 0.001), and diet x gestational day (F[2,463] = 5.34; P < 0.001). No significant main effects or interactions involving the sex of the fetus were observed: however, we chose to present the data by sex (Fig. 2Go) since our original hypothesis involved a sex difference in fetal CORT in response to maternal manipulations, and also because the interaction of ADX, diet, gestational day, and sex shows a trend (F = 2.51, P = 0.08).



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  		Figure 2. Fetal plasma CORT levels in males (A) and females (B). Fetuses are derived from dams described in Fig. 1Go. Abbreviations are as in Fig. 1Go. Plasma CORT was measured in individual fetuses. *, P < 0.05; **, P < 0.01 comparison between diet groups; {dagger}, P < 0.05; {ddagger}, P < 0.01 comparison between ADX and Sham groups.

 
Interestingly, plasma CORT levels of fetuses of ADX dams were not yet elevated at G18, but rose significantly (P < 0.01) on G19 and G21 in fetuses of both groups of ADX dams compared with levels measured in fetuses from dams with intact adrenals. As indicated by the significant ADX x gestational day interaction, post hoc analyses confirmed that fetal CORT levels in both ADX groups were significantly elevated on G19 and G21 compared with levels measured on G18 (P < 0.05). No significant change during this period was detected in fetal plasma from intact dams. Ethanol consumption by the ADX dams reduced the fetal rise in CORT levels compared with the rise observed in fetuses from ADX/PF dams. In the absence of maternal adrenals, plasma CORT levels in FAE male fetuses were significantly lower (P < 0.01) on G19 compared with those measured in PF males. In FAE females from ADX dams, plasma CORT levels were significantly lower (P < 0.05) on G21 compared with PF counterparts.

Maternal-fetal DHEA levels
Plasma DHEA levels of intact dams exhibited a significant surge on G19 (P < 0.05) compared with plasma levels observed on G18 or G21 (Fig. 3Go). No effects of ethanol treatment were observed on this maternal DHEA surge. The ANOVA revealed significant main effects for gestational day (F[2,49] = 40.31; P < 0.01) and ADX (F[1,49] = 38.01; P < 0.001) as well as an interaction between the two factors (F[2, 49] = 78.12; P < 0.001). As shown in Fig. 3Go, there is a clear absence of the plasma DHEA surge on G19 in ADX dams, as plasma DHEA levels are significantly (P < 0.01) lower in the ADX compared with the Sham dams. However, by G21, DHEA plasma levels rose significantly (P < 0.05) in ADX/FAE dams compared with G18 and G19 and in ADX/PF dams compared with G18. Plasma DHEA levels were significantly (P < 0.01) higher in the ADX/FAE dams on G21 compared with both Sham/FAE and Sham/PF dams.



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  		Figure 3. Plasma DHEA levels in pregnant dams during the late period of gestation. Abbreviations are as in Fig. 1Go. {dagger}, P < 0.05; {ddagger}, P < 0.01 comparison between ADX and Sham groups.

 
To determine whether DHEA levels in the fetus mirrored the rise observed in the dam, we measured plasma DHEA levels in Sham/PF and Sham/FAE female fetuses on G19 and G21. Measurements were taken from plasma samples pooled within a litter. Measurement of fetal plasma DHEA on G18 was not done, due to the lower volume of fetal plasma available. In contrast to the significant DHEA surge observed in maternal plasma on G19, fetal plasma levels of DHEA were found to be lower on G19 than on G21 (G19/PF: 0.130 ± 0.02, G19/FAE: 0.035 ± 0.019, G21/PF: 0.179 ± 0.039, G21/FAE: 0.248 ± 0.013 ng/ml DHEA; F[1,10] = 17.67, P < 0.01) An alcohol effect was also detected as indicated by the interaction between diet and gestational day (F[1,10] = 6.92; P < 0.05). This interaction could be seen by the significant (P < 0.01) increase of plasma DHEA from G19 to G21 in the FAE but not in the PF female fetuses.

Fetal-maternal T levels
Prenatal ethanol exposure and/or ADX attenuated the prenatal T surge that normally occurs in male fetuses on G18-G19 (Fig. 4Go). No evidence of a plasma T surge was observed in female fetuses from any of the four groups (data not shown). The ANOVA revealed significant main effects for sex (F[1,106] = 30.93; P < 0.001), diet (F[1,106] = 8.97; P < 0.005), ADX (F[1,106] = 22.12; P < 0.001), and gestational day (F[2,106] = 17.99; P < 0.001).



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  		Figure 4. Plasma T levels in male fetuses of dams described in Fig. 1Go. Fetal plasma was pooled within the litter by sex and analyzed statistically by litter. *, P < 0.05; **, P < 0.01 comparison between diet groups; {dagger}, P < 0.05; {ddagger}, P < 0.01 comparison between ADX and Sham groups.

 
Significant meaningful interactions observed in the ANOVA included the following: ADX x diet (F[1,106] = 9.78; P < 0.005); ADX x gestational day (F[2,106] = 6.45; P < 0.005); diet x gestational day (F[2,106] = 3.18; P < 0.05); and ADX x diet x gestational day (F[2,106] = 3.56; P < 0.05). Maternal ADX significantly (P < 0.01) decreased plasma T levels in PF male fetuses on G18 and G19. In contrast, in FAE fetuses the already attenuated T surge did not decrease further.

Plasma T levels of Sham and ADX males were subsequently analyzed in separate analyses. The analysis of T levels in Sham males revealed significant main effects for diet (F[1,25] = 8.12; P < 0.01) and gestational day (F[2,25] = 8.39; P < 0.01). Post hoc analyses showed significantly elevated plasma T levels in Sham/PF males on G18 and G19 compared with G21 (P < 0.05), indicating the presence of a robust prenatal T surge that normally occurs at this gestational age. A similar rise in T was not observed in Sham/FAE males. Although there was a trend toward higher plasma T levels on G18 in Sham/FAE males compared with levels observed in this group on G19 and G21, the differences were not statistically significant.

Analysis of T levels in males from ADX dams revealed a significant main effect of gestational day (F[2,33] = 4.68; P < 0.025) and a diet x gestational day interaction (F[2,33] = 10.76; P < 0.001). Post hoc analysis showed a significant rise (P < 0.05) in T levels on G19 in ADX/PF males compared with levels observed on both G18 and G21, indicating a small T surge in this group. Levels in ADX/FAE animals did not differ significantly across days.

Maternal plasma T levels were also measured on G19. There were no significant differences between treatment groups (Sham/PF: 0.20 ± 0.03, Sham/FAE: 0.26 ± 002, ADX/PF: 0.17 ± 0.06, ADX/FAE: 0.18 ± 0.05 ng/ml).


   Discussion
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
References
 
Several new findings have emerged from this study, but they afford more questions than answers regarding how maternal alcohol consumption results in sexually dimorphic immunosuppressive effects in the offspring. First is the novel demonstration of a surge of DHEA in the maternal plasma on G19 and its elimination by maternal adrenalectomy. Second, maternal adrenalectomy did not correct, but rather exacerbated, the ethanol-induced suppression of the fetal T surge in males. Finally, no significant sex differences were observed in fetal plasma CORT levels in fetuses exposed to maternal ADX or ethanol.

This is the first report of the presence of DHEA in the rat maternal plasma. On G19, maternal plasma levels rose approximately 3-fold over those observed on G18 and returned to G18 levels by G21. The DHEA surge exhibited on G19 was equivalent in PF and FAE dams but was completely absent in ADX dams from both groups. On G21, a small rise was observed in ADX dams, which likely reflects the direct or indirect contribution of increased fetal adrenal activity in the absence of the maternal adrenal rather than a delay in the appearance of the DHEA surge on G19 observed in intact dams. That this rise is of fetal origin is also supported by the observation of higher DHEA levels in the female fetal plasma on G21 compared with G19, even in the female fetus of dams with intact adrenals. A rise similar to the maternal DHEA rise occurs in maternal plasma CORT levels of ADX dams on G21 and that rise is of fetal origin (24).

From these data it cannot be determined whether the adrenal gland of the pregnant rat produces DHEA or whether placental or gonadal synthesis of DHEA is induced by CORT. P450c17 enzyme is present in the female rat adrenal at low levels, and its activity is enhanced, although only slightly, by ACTH (22). Moreover, in vitro studies using dispersed adrenal cells from adult female rats show that ACTH can stimulate the secretion of adrenal DHEA (23). Alternatively, placental expression of bovine P450c17 has been shown to be induced by fetal or exogenously administered glucocorticoids (25), a phenomenon that seems to be similar in the rat (26), particularly since the promoter of the rat P450c17 gene includes a glucocorticoid-responsive element (27). Therefore, maternal ADX could delay the induction of this enzyme in the placenta until the fetal adrenal is fully functioning. Since maternal DHEA levels of ADX dams seem to increase toward the end of gestation, this DHEA could be of placental origin.

Although the origin of the maternal plasma DHEA is unknown, it could be potentially important in the development of FAE-induced immunosuppression. Administration of exogenous DHEA to adult rodents is known to affect immune function by counteracting the effects of glucocorticoids (28, 29). Although the effect of DHEA in the adult animal seems to be beneficial, it may produce entirely different effects in the developing fetus. The maternal adrenal in humans and baboons provides DHEA for placental estrogen synthesis (30). Administration of androstenedione to pregnant rhesus monkeys also led to increased maternal plasma estradiol (31). Increased estrogen production has been shown to enhance placental 11ß-hydroxysteroid dehydrogenase oxidase production (32, 33). The increased 11ß-hydroxysteroid dehydrogenase production can activate fetal pituitary-adrenal function by increasing the transplacental corticosteroid metabolism and thereby removing the negative feedback of maternal glucocorticoids (32). Thus, DHEA prenatally may actually promote the production of fetal CORT and alter the development of the immune system. We have recently found that maternal DHEA treatment results in decreased T cell function in the male offspring (34), similar to effects observed following FAE (13), suggesting a role for maternal DHEA in development.

The results from this study also reveal the major importance of a maternal adrenal factor in eliciting the prenatal T surge. The prenatal surge of T normally occurs on G18–19 in rats and is considered to be an integral part of the complete neurobehavioral masculinization and defeminization of the male brain (6, 7). Male fetuses from intact PF dams exhibited the normal prenatal surge that we and others have previously observed in males from both PF and untreated dams (9, 10, 35). In contrast, male fetuses from ADX dams exhibited a marked attenuation of a T surge during this period. These results indicate that a maternal adrenal factor is a critical element in the maintenance of this surge, but whether its influence is on the fetal pituitary-gonadal axis or on the placenta, by perhaps influencing the production of steroid metabolizing enzymes, is unknown.

The timing of the maternal DHEA surge is coincident with the surge in fetal plasma T, although it appears to be more restricted to G19. Since DHEA is a precursor for androgens such as T, it is intriguing to consider the possibility that the maternal DHEA surge may contribute to the surge in fetal T. However, this appears unlikely based upon the present results showing a surge in fetal T on G18 in fetuses of PF dams that precedes the maternal DHEA rise. Although maternal CORT, or lack thereof, would be the most likely candidate for the adrenal factor modulating the rise in both maternal plasma DHEA and fetal T, its potential role is not clear from the present results.

Maternal plasma CORT levels remained elevated during the period from G18–21 in FAE dams, but in PF dams there was a drop on G19 compared with G18 and G21. During this period, the plasma DHEA surge did not differ between the PF and FAE dams, but the plasma T surge in FAE males from intact dams was attenuated similarly to our previous results (9). Since maternal ADX also attenuated the fetal surge of T, the FAE-induced decrease in the fetal T surge may not be related to alcohol-induced elevations in maternal CORT. Alternatively, the compensatory elevations of fetal CORT after maternal ADX may inhibit fetal T production (36). Replacement studies of CORT in ADX dams will be helpful in determining the role of CORT in the induction of the maternal DHEA and the fetal T surge.

There were no sex differences in fetal CORT levels in offspring of Sham or ADX dams. Furthermore, maternal ethanol consumption did not alter fetal CORT levels differentially in male and female fetuses. However, since during late gestation fetal corticosteroid binding globulin (CBG) is regulated independently from the mother’s (37), and CBG production could be regulated by gonadal steroids (38, 39), free CORT levels may still differ between male and female fetuses. T administration to castrated adult males decreases CBG content by 50% (39), while neonatal gonadectomy increases CBG levels (38). Therefore, during the prenatal surge of T, CBG levels may be lower in the male fetus compared with the female, leaving higher free CORT levels in the male compared with the female, and thereby making males more vulnerable to environmental insult. Thus, if free CORT levels change linearly with T, then even the FAE-attenuated T surge could increase the amount of free CORT and thereby affect fetal functions in the FAE male. However, in the absence of maternal glucocorticoids, when the fetal T surge is attenuated similarly to that in FAE, male fetuses are no longer affected by prenatal alcohol exposure, suggesting that elevated maternal glucocorticoids are critical.

While ethanol significantly stimulated CORT production in intact dams, in the present study we did not detect the previously observed significant inverse relationship between maternal and fetal glucocorticoid levels (10). This discrepancy may be due to the somewhat higher maternal CORT levels in these PF dams together with lower fetal CORT in their fetuses, compared with our previous study; as a result, the difference between FAE and PF dams with intact adrenals and their fetuses is decreased in the present study. However, the inverse relationship between fetal and maternal CORT could be clearly seen in offspring of ADX dams.

Fetal CORT levels increased dramatically at G19 and G21 in offspring of ADX dams. This compensatory mechanism is a well established phenomenon (37, 40) and is likely to be the cause of the elevated CORT levels that appear in the maternal plasma by G21. Plasma CORT levels in fetuses of ADX dams were not yet elevated on G18, suggesting that functioning of the fetal adrenal does not occur before G18. Before this, CORT crosses the placenta from the maternal to the fetal circulation (41), so that elevated maternal CORT levels before G18 may subsequently affect the functioning of the fetal adrenal later in development. In addition to suppressing the fetal corticotrope activity, since POMC transcription is already responsive to glucocorticoids at this age (42), elevated maternal glucocorticoids may suppress the production of fetal CBG.

A new and important finding that emerges from this study is that the inhibitory effect of ethanol on fetal CORT secretion can be unmasked in the fetuses of ADX/FAE dams. Here the decrease in fetal CORT secretion of FAE offspring of ADX dams occurs after G18 and suggests that it is a direct effect of ethanol on the fetal pituitary-adrenal function. The mechanism responsible for this decreased CORT production in ADX/FAE fetuses is not known.

In summary, we found no evidence for sex differences in the effects of ethanol or maternal ADX on fetal CORT levels, implying the involvement of additional sex-specific events leading to the sex differences found in the effects of FAE on the developing fetus. Since maternal ADX abolished ethanol-induced elevations in maternal CORT levels as well as attenuated the fetal T surge, male-specific vulnerability to FAE may be related to the combined effects of fetal T and elevated maternal CORT on the development of the male fetus. The role, origin, and physiological significance of the maternal surge of DHEA remains to be determined.


   Footnotes
 
1 This work was supported by National Institute of Alcoholism and Alcohol Abuse Grant AA-07389. Back

Received January 24, 1997.


   References
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 References
 

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