EFFECTS OF ESTROGEN AND PROGESTERONE ON PLATELET-ACTIVATING-FACTOR ACETYLHYDROLASE ACTIVITY IN OVARIECTOMIZED RATS

Objective: To evaluate the effect of estrogen and progesterone on plas ma platelet-activating factor acetylhydrolase (PAF-AH) activity in ova riectomized rats. Methods: Plasma PAF-AH activity was examined in ovar iectomized 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 2.50% and 3.4%, respectively. Plasma lipoprotein profiles on day 5 were dete rmined with commercially available kits. Results: Ovariectomized rats showed no significant change in plasma PAF-AH activity over a 14 day p eriod. Estrogen decreased the PAF-AH activity up to 85%, and progester one increased PAF-AH activity up to 44% in ovariectomized rats. There was a positive correlation between plasma PAF-AH activity and high den sity lipoprotein cholesterol (r= 0.96, p<0.001). Conclusion: These dat a suggest that estrogen and progesterone exert an effect on plasma PAF -AH activity in ovariectomized rats, possibly via high density lipopro tein cholesterol.