Effects of levonorgestrel on enzymes responsible for synthesis of triacylglycerols in rat liver.
The effects of levonorgestrel treatment (4 micrograms/day per kg body weight 0.75 for 18 days) on rate-limiting enzymes of hepatic triacylglycerol synthesis, namely glycerol-3-phosphate acyltransferase and phosphatidic acid phosphatase were investigated in microsomal, mitochondrial and cytosolic fractions of rat liver. Levonorgestrel treatment resulted in a significant reduction (26%) of hepatic microsomal glycerol-3-phosphate acyltransferase specific activity. Hepatic mitochondrial glycerol-3-phosphate acyltransferase specific activity was unchanged. Levonorgestrel treatment also significantly reduced (by 20%) the specific activity of hepatic microsomal magnesium-independent phosphatidic acid phosphatase. However, magnesium-dependent phosphatic acid phosphatase specific activities in microsomal and cytosolic fractions were unaffected. Cytosolic magnesium-independent phosphatidic acid phosphatase activity was also unchanged. These studies are consistent with the view that levonorgestrel lowers serum triacylglycerol levels, at least in part, by inhibition of the glycerol-3-phosphate acyltransferase (EC 2.3.1.15) step in hepatic triacylglycerol synthesis.
D000818:Animals; D005260:Female; D005992:Glycerol-3-Phosphate O-Acyltransferase / Q000037:antagonists & inhibitors / Q000378:metabolism; D005994:Glycerophosphates / Q000378:metabolism; D016912:Levonorgestrel; D008099:Liver / Q000201:enzymology*; D009644:Norgestrel / Q000494:pharmacology*; D010711:Phosphatidate Phosphatase / Q000037:antagonists & inhibitors / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D013347:Subcellular Fractions / Q000201:enzymology; D014280:Triglycerides / Q000096:biosynthesis*
D005994:Glycerophosphates; D014280:Triglycerides; D009644:Norgestrel; D016912:Levonorgestrel; C029620:alpha-glycerophosphoric acid; D005992:Glycerol-3-Phosphate O-Acyltransferase; D010711:Phosphatidate Phosphatase