The effect of contraceptive steroids on plasma lipoprotein metabolism in female rats (II).

In order to investigate the effects of two contraceptive steroids given orally, which contain ethinyl estradiol in combination with different types and doses of progestins, on plasma lipoprotein metabolism, rat groups named according to progestin components were designated as short-and long-term groups of norethisterone acetate and levonorgestrel at low-and high-doses. At the end of the experiments, plasma triglyceride, phospholipid, apolipoprotein A1 and B, LDL-, HDL-, HDL2- and HDL3-cholesterol levels and hepatic lipase activity were measured. When compared to controls, phospholipid and LDL-cholesterol were increased in all groups; triglyceride levels were also increased in all short-term groups, but only in low-dose norethisterone and high-dose levonorgestrel of long-term groups. HDL- and HDL3- cholesterol were decreased in all groups, except in low-dose levonorgestrel groups, but HDL2-cholesterol were lower only at high doses and long period. In short-term, an increase in apolipoprotein A1 levels was significantly important at high doses; in long-term apolipoprotein A1 was increased at low doses, while decreased at high doses. Apolipoprotein B was elevated only in long-term high dose of norethisterone acetate group. Hepatic lipase activity was increased in long-term high-dose of levonorgestrel group, whereas decreased in all other groups. In conclusion, the data presented was interpreted that the effects of these combinations used in the study on plasma lipoprotein metabolism may be related to the changes observed in hepatic lipase activity.