Hypotriglyceridemic effects of levonorgestrel in rats

The progestin, levonorgestrel administered orally to fed female rats significantly lowers both plasma total and very low density lipoprotein triglycerides. In contrast, plasma total cholesterol and low density lipoprotein cholesterol rose significantly. Suspensions of isolated hepatocytes were used to study the effects of levonorgestrel on triglyceride synthesis by examining the incorporation of labelled precursors [( 9,10- 3H]palmitate and [U-14C]glycerol) into triglycerides. Levonorgestrel (10(-4) M) significantly inhibited the incorporation of both precursors into hepatocyte triglycerides and also reduced their incorporation into the triglycerides (nearly all in d less than 1.006) released into the medium. These results suggest that inhibition of hepatic triglyceride synthesis and release can account at least for part of the lowering of plasma VLDL which occurs during administration of levonorgestrel.