Objective: To evaluate the effect of estrogen and progesterone on plasma platelet-activating factor acetylhydrolase (PAF-AH) activity in ovariectomized rats.
Methods: Plasma PAF-AH activity was examined in ovariectomized rats treated with 17 alpha-ethynylestradiol (0.25 mg/kg; 6 days) or medroxyprogesterone (50 mg/kg; 6 days). The intra- and inter-assay coefficients of variation for plasma PAF-AH activity were 2.5% and 4.4%, respectively. Plasma lipoprotein profiles on day 5 were determined with commercially available kits.
Results: Ovariectomized rats showed no significant change in plasma PAF-AH activity over a 14 day period. Estrogen decreased the PAF-AH activity up to 85%, and progesterone increased PAF-AH activity up to 44% in ovariectomized rats. There was a positive correlation between plasma PAF-AH activity and high density lipoprotein cholesterol (r = 0.96, p < 0.001).
Conclusion: These data suggest that estrogen and progesterone exert an effect on plasma PAF-AH activity in ovariectomized rats, possibly via high density lipoprotein cholesterol.