| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
ARTICLES |
Department of Veterinary Preclinical Sciences, University of Glasgow Veterinary School (P.J.O., P.B.), Glasgow, Scotland G61 1QH; the Department of Human Anatomy, University of Oxford (U.S., H.M.C.), Oxford, United Kingdom OX1 3QX; and the Department of Physiology, University of Turku (A.-M.H., I.H.), 20520 Turku, Finland
Address all correspondence and requests for reprints to: Prof. P. J. O’Shaughnessy, Department of Veterinary Preclinical Sciences, University of Glasgow Vet School, Bearsden Road, Glasgow, Scotland G61 1QH. E-mail: P.J.OShaughnessy{at}vet.gla.ac.uk
 |
Abstract |
|---|
 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
-hydroxylase increased
from E13 to reach a peak around birth. In hpg mice,
levels of mRNA encoding these enzymes were normal until around birth,
at which time there was a significant decline. Levels of testicular
mRNA encoding 3ß-hydroxysteroid dehydrogenase type I were similar in
normal and hpg mice and showed little change during
development. Intratesticular testosterone reached a peak on E18 in
normal animals before declining again after birth. In
hpg mice, intratesticular testosterone levels were
normal throughout fetal development and on the day of birth, but were
barely detectable by postnatal day 5. Results show 1) that fetal Leydig
cell function in the mouse is normal in the absence of endogenous
circulating gonadotropins; 2) that Leydig cells become dependent on
gonadotropins shortly after birth; and 3) that pituitary LH synthesis
can start in the absence of GnRH but is dependent on LH for a normal
level of synthesis and secretion |
Introduction |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
The fetal anterior pituitary is derived from Rathke’s pouch, which is first identifiable in the mouse on E8 (7). Proliferation and differentiation of ectodermal cells gives rise to five distinct cell types, which are identified by the hormones they produce. GnRH neurons first appear in the hypothalamus around E14 (8), whereas transcripts of the LHß gene are first detected by in situ hybridization in the gonadotrophs on about E16 (9). All the components of an active hypothalamic-pituitary axis are present, therefore, around E16, although it is not clear whether LH is produced at this time in the mouse pituitary and whether it is under GnRH control.
Evidence from the timing of fetal pituitary/testicular development and
from organ culture experiments makes it appear likely that the early
phase of Leydig cell function is pituitary independent (10, 11, 12). This
is supported by observations in both hypogonadal (hpg) mice
that lack GnRH and in mice with targeted disruption of the common
-subunit (13, 14). In both of these mutants endogenous circulating
gonadotropins are undetectable, yet differentiation of the male tract
occurs during fetal development. Nevertheless, the later peak of fetal
androgen production occurs in the mouse after differentiation of the
pituitary gonadotrophs and expression of the LHß gene, suggesting
that Leydig cell function in the later fetal period might be under
pituitary regulation. In this study we have examined the fetal
development of pituitary LH levels and Leydig cell function in normal
mice and in hpg mice. This has allowed us to determine the
time at which the hypothalamic-pituitary axis develops in the mouse and
to examine the role of the fetal pituitary in regulating Leydig cell
function.
|
Materials and Methods |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Assay for LH and testosterone
To measure pituitary content of LH, fetal pituitaries were
homogenized in 100 µl 0.1% PBS-BSA and assayed using a highly
sensitive dissociation-enhanced lanthanide fluorometric immunoassay
(DELFIA, Wallac, Turku, Finland) as previously described (16). The
sensitivity of the assay is 0.03 ng/ml, and cross-reactivity is 0.3%
with rat FSH, 3% with rat TSH, and less than 0.05% with rat GH and
PRL. The testosterone content of the testes was measured by RIA after
extraction with ethanol as previously described (17).
RT-PCR
Total RNA was extracted from testes of individual animals using
RNAzol (Biogenesis, Poole, UK). RNA was reverse transcribed using
random hexamers and Moloney murine leukemia virus reverse transcriptase
(SuperScript, Life Technologies, Paisley, UK) as previously described
(18, 19). The PCRs were carried out in Tris-HCl buffer (75
mM, pH 9.0, at 25 °C) containing
(NH4)2SO4 (20 mM),
Tween (0.01%), MgCl2 (2 mM), deoxy-NTPs (0.2
mM each), Taq polymerase (2 U/100 µl), primers
(200 nM each), and template (0.1–2 µl) in a total
incubation volume of 30 µl.
To assess Leydig cell function, messenger RNA (mRNA) levels encoding
the steroidogenic enzymes 3ß-hydroxysteroid dehydrogenase (3ßHSD),
cytochrome P450 side-chain cleavage (P450scc), and cytochrome P450
17-hydroxylase (P450c17) were measured. In addition, the expression
of LH receptor transcripts was studied using PCR and Southern blotting
(20). The primers used are shown in Table 1
and are all based on published mouse
sequences (21, 22, 23, 24). The mouse 3ßHSD primers were designed to amplify
the type I enzyme but also show 100% homology with the recently
described type VI enzyme (25) and will, therefore, amplify both
isoforms.
|
Southern blotting
For Southern hybridization of LH receptor PCR products, the DNA
was transferred from agarose to nitrocellulose membranes and hybridized
with a 32P-labeled complementary DNA (cDNA) probe prepared
by PCR and extending from exon 1 to exon 9.
Statistics
Results were analyzed using two-way ANOVA and, where
appropriate, further analyzed by t tests using the residual
variance from the initial ANOVA.
|
Results |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
). On E13 and E14, the youngest ages
tested, no full-length LH receptor transcripts were observed, although
a shortened band of about 650 bp was clearly present on day E13 and
less intensely on E14 (Fig. 1B). From E16 onward, full-length receptor
transcripts were detectable at all ages tested. At each age, a number
of shorter transcripts were also present, although the length of these
transcripts varied from age to age. The most common transcript, present
in all fetal testes, was about 650 bp (Fig. 1B). There was no clear
difference in expression of LH receptor transcripts between normal mice
and hpg mice during development from E16 to day 1 (Fig. 1C).
In this experiment two major bands were seen in all groups
corresponding to full-length transcripts and a shortened, 650-bp
transcript. Smaller transcripts were also seen in some animals.
|
). Levels remained close to the limit of
detection of the assay in both groups on E16 before starting to rise on
E17. From E17, levels of pituitary LH were significantly and markedly
lower in the hpg group than those in normal animals,
although there was a clear age-dependent increase in hormone levels in
both groups (Fig. 2).
|
) produced a single band of the
correct size (Fig 3A). Using
semiquantitative methods, cytochrome P450scc mRNA was detectable on E13
and at all subsequent ages in both normal and hpg mice (Fig. 3B). In normal mice there was an increase in P450scc levels from E13 up
until the day of birth (day 1) and a decline, thereafter, to day 5.
Levels of P450scc mRNA in hpg mice were normal up to E18,
but were significantly reduced compared with normal values on days 1
and 5 after birth (Fig. 3B).
|
to amplify 3ßHSD
type I/VI from testicular cDNA, a single product of the correct size
was obtained (Fig. 3A). Using semiquantitative RT-PCR methods, 3ßHSD
mRNA was detectable at all ages tested in both normal and
hpg mice (Fig. 3C). Levels of 3ßHSD mRNA were highly
variable between animals at all ages, and there was no overall change
in mRNA levels relative to ß-actin during development. Similarly,
there was no significant difference in 3ßHSD mRNA levels between
normal and hpg animals.
Cytochrome P450c17. Amplification of P450c17 by PCR yielded a
single product of the correct size (Fig. 3A). In common with P450scc
and 3ßHSD, P450c17 mRNA was detectable using semiquantitative RT-PCR
at all ages tested (Fig. 3D). In both normal and hpg
animals, levels of P450c17 increased from E13 to a peak on E18 before
declining again after birth. In hpg mice, levels of P450c17
were significantly lower than normal on E18 and declined markedly at
birth to remain significantly less than normal up to 5 days (Fig. 3D).
Testosterone. In normal mice levels of intratesticular
testosterone reached a peak during fetal development on E18 before
declining again after birth (Fig. 4A).
There was no significant difference in testosterone levels between
normal and hpg animals during fetal life. After birth, there
was considerable variation in levels of intratesticular testosterone in
normal mice (Fig. 4B). In hpg mice it is more clear that
levels of testosterone were declining from the high on E18, and by
postnatal day 5, levels were barely detectable (Fig. 4, A and B). Due
to the high variability, there was no significant difference between
normal and hpg mice until postnatal day 5.
|
|
Discussion |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
The fetal testis produces relatively high levels of androgen, which are
vital for differentiation of the internal and external male phenotype
(5). Both hpg mice and mice with disruption of the common
pituitary -subunit show a normal male phenotype at birth (13, 14),
demonstrating that androgens must be released by the fetal testis in
the absence of circulating gonadotropins. Evidence from the present
study shows that testicular androgen synthesis and Leydig cell function
are largely normal throughout the fetal period in the absence of
detectable endogenous gonadotropins. These results suggest either that
the Leydig cells are constitutively active during early development or
that an unknown factor maintains and stimulates Leydig cell function
during at least part of fetal life. In rodents, there is no LH/CG-like
gene expressed in the placenta, indicating that factors stimulating
Leydig cell function are unlikely to come from this source (30, 31).
The nature of a potential stimulatory factor is unknown,
therefore, although it seems likely that it would be locally
produced, probably by the developing Sertoli cells. A number of
paracrine factors, including growth factor families (32), Desert
hedgehog (33), tissue inhibitor of metalloproteinase-1/procathepsin
(34), and D-aspartic acid (35), have been implicated in
the regulation of Leydig cell function, while vasoactive intestinal
peptide and pituitary adenylate cyclase-activating polypeptide have
been shown to have stimulatory effects on fetal Leydig cells, but not
adult cells (12). It remains to be shown, however, whether any of these
factors are required for normal Leydig cell function during fetal
development. Whether paracrine factors serve to stimulate Leydig cell
function during fetal life independence of the developing Leydig cells
from pituitary gonadotroph function may act as a developmental
safeguard to ensure normal virilization of the male fetus.
Evidence from other species concerning involvement of endogenous gonadotropins in fetal Leydig cell function is less clear-cut. Studies of fetal rabbit testes in organ culture suggest that initiation of testosterone synthesis in this species is gonadotropin independent (10), which is consistent with the results presented here. In apparent contrast, humans with inactivating mutations in the LH receptor develop an external female phenotype (36). These individuals, however, also form epididymides and ductus deferens, both of which are derived from the mesonephric duct. The failure of external masculinization in these cases may be caused by a relative delay in external sexual differentiation in humans. In mice, both internal and external virilization occur rapidly, within a few days of testis differentiation. In the human, differentiation of the male phenotype occurs over a longer period (20–30 days), suggesting that the fetal testis can secrete androgens in the absence of LH stimulation, but that this secretion is limited to the early stages of testicular development. Earlier studies on human fetal testis activity in vitro also indicated that the onset of testosterone synthesis may be independent of LH (37). This is consistent with the data presented here on testis development in the hpg mouse, suggesting an early gonadotropin-independent phase of development followed by a requirement for gonadotropin stimulation. Differences in sexual differentiation between humans with mutations in the LH receptor and hpg mice could also arise because the normal LH receptor shows endogenous activity in the absence of ligand binding. In that case it may be that it is inactivation of the receptor rather than inhibition of hormone action that prevents normal Leydig cell development. It is worth noting that an inactivating mutation of the human LH ß-subunit has been described in which normal male differentiation occurs, although this is likely to be due at least in part to the presence of hCG in the human (38).
After birth, there was a marked decline in Leydig cell function in hpg mice. This was clear from loss of expression of the enzymes P450scc and P450c17 and from the decline in intratesticular testosterone to barely detectable levels by day 5. There was also a decline in P450c17 mRNA levels and intratesticular testosterone in normal animals, but this was not as marked. These results show that endogenous gonadotropins become essential for normal Leydig cell function in the perinatal period. Thus, around birth, there is a switch from constitutive Leydig cell activity or dependence on paracrine stimulation to dependence upon circulating gonadotropins. It is worth noting that full-length LH receptor transcripts appear in the testis on day E16, that LH production starts in the pituitary at about this time, that circulating levels of LH mirror pituitary levels in normal animals (12), and that fetal testes can respond to LH in vitro on E16 (39, 40). This indicates that in the latter part of fetal life it is likely that there is potential dual support of Leydig cell function. What induces the change to gonadotropin dependence is not clear, but may be related to birth itself, to changes in Leydig cell function as the fetal population starts to be replaced by the adult population (41), or to changes in Sertoli cell function as spermatagonia start to differentiate (41).
In both normal and hpg mice, expression of steroidogenic enzymes was relatively high on day E13, shortly after testis differentiation. This confirms a previous study showing early onset of expression of the steroidogenic enzymes in the developing Leydig cells (43) and indicates that differentiating Leydig cells show a very rapid capacity for steroidogenesis. Development of LH receptor transcript expression in the developing normal and hpg mouse testis was similar to that described previously in the rat (44), although first expression of full-length transcripts in the rat was slightly earlier, on E15.5, which is equivalent to about E14/14.5 in the mouse. At each age measured it was clear that a number of alternate transcripts were also present, although expression varied between animals, and their physiological significance is, therefore, uncertain. The most common alternative transcript seen in all fetal testes was of 650 bp, which would correspond to a transcript missing exons 2–6, which has already been described in the mouse ovary (20). Interestingly, this transcript was expressed from E13, shortly after Leydig cell differentiation. Whether such a transcript lacking exons 2–6 would transduce hormone action is not known, but it is possible that Leydig cells are sensitive to hormone from a very early stage. This would be supported by in vitro studies demonstrating that testes from mice on E14 show a small, but significant, rise in testosterone production in response to hCG (39). Such receptors are unlikely to have any functional role, however, as LH is not produced by the pituitary at this time.
In summary, the results show that in the mouse, Leydig cell function during fetal development is independent of gonadotropin stimulation. It remains to be shown whether Leydig cells are constitutively active during this time or whether paracrine factors serve to regulate androgen production. In the latter part of fetal life, the pituitary-gonadal axis is well developed, and it is possible that there is dual control of Leydig cell function. Around birth, gonadotropins become essential for maintenance of normal testicular androgen levels, showing that the emphasis of Leydig cell control has moved to the pituitary.
|
Footnotes |
|---|
Received September 16, 1997.
|
References |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
-subunit produces hypogonadal and hypothyroid mice. Genes Dev 9:2007–201-hydroxylase protein and mRNA in the testis of the testicular
feminized (Tfm) mouse. J Mol Endocrinol 11:77–82
5-4 isomerase and
differential expression in gonads, adrenal glands, liver, and kidneys
of both sexes. Proc Natl Acad Sci USA 88:8870–8874-hydroxylase C17–20 lyase gene
(cyp17): transcriptional regulation of the gene by cyclic adenosine
3',5'-monophosphate in MA10 Leydig cells. Mol Endocrinol 6:927–934[Abstract]
-hydroxylase C17–20
lyase, and P450 aromatase in fetal mouse gonads. Endocrinology 135:262–268[Abstract]
This article has been cited by other articles:
 |
|
 |
|
  O. E Chausiaux, M. H Abel, F. O Baxter, W. T Khaled, P. J.I Ellis, H. M Charlton, and N. A Affara Hypogonadal Mouse, a Model to Study the Effects of the Endogenous Lack of Gonadotropins on Apoptosis Biol Reprod, January 1, 2008; 78(1): 77 - 90. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 H. Johnston, P. J King, and P. J O'Shaughnessy Effects of ACTH and expression of the melanocortin-2 receptor in the neonatal mouse testis Reproduction, June 1, 2007; 133(6): 1181 - 1187. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 P. J. O'Shaughnessy, M. Abel, H. M. Charlton, B. Hu, H. Johnston, and P. J. Baker Altered Expression of Genes Involved in Regulation of Vitamin A Metabolism, Solute Transportation, and Cytoskeletal Function in the Androgen-Insensitive Tfm Mouse Testis Endocrinology, June 1, 2007; 148(6): 2914 - 2924. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 N. A. Sims, K. Brennan, J. Spaliviero, D. J. Handelsman, and M. J. Seibel Perinatal testosterone surge is required for normal adult bone size but not for normal bone remodeling Am J Physiol Endocrinol Metab, March 1, 2006; 290(3): E456 - E462. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 E. Denolet, K. De Gendt, J. Allemeersch, K. Engelen, K. Marchal, P. Van Hummelen, K. A. L. Tan, R. M. Sharpe, P. T. K. Saunders, J. V. Swinnen, et al. The Effect of a Sertoli Cell-Selective Knockout of the Androgen Receptor on Testicular Gene Expression in Prepubertal Mice Mol. Endocrinol., February 1, 2006; 20(2): 321 - 334. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. M. Apaja, J. T. Aatsinki, H. J. Rajaniemi, and U. E. Petaja-Repo Expression of the Mature Luteinizing Hormone Receptor in Rodent Urogenital and Adrenal Tissues Is Developmentally Regulated at a Posttranslational Level Endocrinology, August 1, 2005; 146(8): 3224 - 3232. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. Simard, M.-L. Ricketts, S. Gingras, P. Soucy, F. A. Feltus, and M. H. Melner Molecular Biology of the 3{beta}-Hydroxysteroid Dehydrogenase/{Delta}5-{Delta}4 Isomerase Gene Family Endocr. Rev., June 1, 2005; 26(4): 525 - 582. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. Delbes, C. Levacher, C. Duquenne, C. Racine, P. Pakarinen, and R. Habert Endogenous Estrogens Inhibit Mouse Fetal Leydig Cell Development via Estrogen Receptor {alpha} Endocrinology, May 1, 2005; 146(5): 2454 - 2461. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 X. Ma, Y. Dong, M. M. Matzuk, and T. R. Kumar Targeted disruption of luteinizing hormone {beta}-subunit leads to hypogonadism, defects in gonadal steroidogenesis, and infertility PNAS, December 7, 2004; 101(49): 17294 - 17299. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. R. Kumar Divide and Differentiate: Ghrelin Instructs the Leydig Cells Endocrinology, November 1, 2004; 145(11): 4822 - 4824. [Full Text] [PDF]
|
|
|
|
|
|
F.-p. Zhang, T. Pakarainen, F. Zhu, M. Poutanen, and I. Huhtaniemi Molecular Characterization of Postnatal Development of Testicular Steroidogenesis in Luteinizing Hormone Receptor Knockout Mice Endocrinology, March 1, 2004; 145(3): 1453 - 1463. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H. Johnston, P. J. Baker, M. Abel, H. M. Charlton, G. Jackson, L. Fleming, T. R. Kumar, and P. J. O'Shaughnessy Regulation of Sertoli Cell Number and Activity by Follicle-Stimulating Hormone and Androgen during Postnatal Development in the Mouse Endocrinology, January 1, 2004; 145(1): 318 - 329. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. A. Spaliviero, M. Jimenez, C. M. Allan, and D. J. Handelsman Luteinizing Hormone Receptor-Mediated Effects on Initiation of Spermatogenesis in Gonadotropin-Deficient (hpg) Mice Are Replicated by Testosterone Biol Reprod, January 1, 2004; 70(1): 32 - 38. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. S. Calikoglu Adrenocorticotropic Hormone, a New Player in the Control of Testicular Steroidogenesis Endocrinology, August 1, 2003; 144(8): 3277 - 3278. [Full Text] [PDF]
|
|
|
|
|
|
P. J. O'Shaughnessy, L. M. Fleming, G. Jackson, U. Hochgeschwender, P. Reed, and P. J. Baker Adrenocorticotropic Hormone Directly Stimulates Testosterone Production by the Fetal and Neonatal Mouse Testis Endocrinology, August 1, 2003; 144(8): 3279 - 3284. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 N. J. Barlow, S. L. Phillips, D. G. Wallace, M. Sar, K. W. Gaido, and P. M. D. Foster Quantitative Changes in Gene Expression in Fetal Rat Testes following Exposure to Di(n-butyl) Phthalate Toxicol. Sci., June 1, 2003; 73(2): 431 - 441. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Haywood, J. Spaliviero, M. Jimemez, N. J. C. King, D. J. Handelsman, and C. M. Allan Sertoli and Germ Cell Development in Hypogonadal (hpg) Mice Expressing Transgenic Follicle-Stimulating Hormone Alone or in Combination with Testosterone Endocrinology, February 1, 2003; 144(2): 509 - 517. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. J. Baker, P. Pakarinen, I. T. Huhtaniemi, M. H. Abel, H. M. Charlton, T. R. Kumar, and P. J. O'Shaughnessy Failure of Normal Leydig Cell Development in Follicle-Stimulating Hormone (FSH) Receptor-Deficient Mice, But Not FSH{beta}-Deficient Mice: Role for Constitutive FSH Receptor Activity Endocrinology, January 1, 2003; 144(1): 138 - 145. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. J. Bianco, D. J. Handelsman, J. S. Pedersen, and G. P. Risbridger Direct Response of the Murine Prostate Gland and Seminal Vesicles to Estradiol Endocrinology, December 1, 2002; 143(12): 4922 - 4933. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. Pakarinen, S. Kimura, F. El-Gehani, L. J. Pelliniemi, and I. Huhtaniemi Pituitary Hormones Are Not Required for Sexual Differentiation of Male Mice: Phenotype of the T/ebp/Nkx2.1 Null Mutant Mice Endocrinology, November 1, 2002; 143(11): 4477 - 4482. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. Ishii, T. Hasegawa, C.-I Pai, N. Yvgi-Ohana, R. Timberg, L. Zhao, G. Majdic, B.-c. Chung, J. Orly, and K. L. Parker The Roles of Circulating High-Density Lipoproteins and Trophic Hormones in the Phenotype of Knockout Mice Lacking the Steroidogenic Acute Regulatory Protein Mol. Endocrinol., October 1, 2002; 16(10): 2297 - 2309. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P.J. O'Shaughnessy, L. Willerton, and P.J. Baker Changes in Leydig Cell Gene Expression During Development in the Mouse Biol Reprod, April 1, 2002; 66(4): 966 - 975. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 P. J. O'Shaughnessy, H. Johnston, L. Willerton, and P. J. Baker Failure of normal adult Leydig cell development in androgen-receptor-deficient mice J. Cell Sci., January 9, 2002; 115(17): 3491 - 3496. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S.M.L. Chamindrani Mendis-Handagama and H.B. Siril Ariyaratne Differentiation of the Adult Leydig Cell Population in the Postnatal Testis Biol Reprod, September 1, 2001; 65(3): 660 - 671. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
F.-P. Zhang, M. Poutanen, J. Wilbertz, and I. Huhtaniemi Normal Prenatal but Arrested Postnatal Sexual Development of Luteinizing Hormone Receptor Knockout (LuRKO) Mice Mol. Endocrinol., January 1, 2001; 15(1): 172 - 183. [Abstract] [Full Text]
|
|
|
|
 |
|
 L Zhao, M Bakke, Y Krimkevich, L. Cushman, A. Parlow, S. Camper, and K. Parker Steroidogenic factor 1 (SF1) is essential for pituitary gonadotrope function Development, January 1, 2001; 128(2): 147 - 154. |
