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Effects of Ethynyl Estradiol and Progesterone on Triglyceride Metabolism in the Female Rat^*

Service d'Explorations Métaboliques, Hospital de la Conception 13385 Marseille, Cedex 4, France>

Address reprint requests to: Dr. J. Boyer, Service d'Explorations Metaboliques, Hôpital de la Conception, 13385 Marseille, Cedex 4, France

Abstract

Several lipase activities in adipose tissue and liver as well as triglyceride content in liver and blood were concomitantly investigated in adult female rats after 21 days of oral treatment with ethynyl estradiol (6 fig daily), progesterone (5 µg daily), or the two steroids in combination.

Treatment with ethynyl estradiol alone markedly decreased the levels of all lipase activities assayed at acid Qnd alkaline pH levels in liver fractions. Decreases in enzyme activities were associated with a 39% increase in blood triglyceride levels. The administration of progesterone alone did not modify triglyceride level in blood or liver lipase activities. The combined regimen of ethynyl e$tradiol plus progesterone caused maximal decreases in hepatic lipases, a 29% decrease in the triglyceride content of liver, but no change in the level of triglycerides in blood. Studies in adipose tissue showed that treatment with ethynyl estradiol and progesterone, separately or in combination, increased lipoprotein lipase activity to a comparable extent. After treatment with progesterone alone, the increase was observed in the absence of elevated levels of triglycerides in blood. Triacylglycerol lipase activity assayed at pH 7.4 (hormone- sensitive lipase) was not affected by ethynyl estradiol or progesterone alone, but a significant decrease was observed under a combined regimen. None of these hormonal treatments modified the level of monoester lipase activity.

Taken together, the results point to major hormonal influences on lipid metabolism in liver and adipose tissue. However, it cannot be assessed whether these effects are due to the direct action of ethynyl estradiol and progesterone on liver and adipose tissue lipases and/or to some other altered metabolic response (s) secondary to the intake of the steroids.

Footnotes

^* This study was supported by grants from DGRST (no. 75.7.0033) and INSERM (no. 74.2.469.30.9) and by La Fondation pour la Recherche Medicale Francaise

Received November 14, 1977.

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