The effect of acetylsalicylic acid and captopril on uterine and ovarian blood flow during the estrous cycle in mares

Abstract

In previous studies, transrectal color Doppler sonography was used to demonstrate an increase in genital blood flow resistance in subfertile mares. The objectives of the present study were to determine the effects of an anticoagulant (acetylsalicylic acid) and a vasodilator (captopril) on uterine and ovarian perfusion and plasma progesterone concentrations in cycling mares. From Day 1 to 11 of an estrous cycle (Day 0=day of ovulation following prostaglandin-induced luteolysis), five Trotter mares were given 2500 mg lactose, 2500 mg ASA, or 50 mg captopril twice daily in their feed (one compound per cycle, in random order). Transrectal color Doppler sonography was used to examine both uterine arteries and the ovarian artery ipsilateral to the corpus luteum once daily, immediately prior to administration of the drug. Blood flow resistance was determined semiquantitatively using the pulsatility index (PI) and plasma progesterone concentrations were determined with an enzyme immunoassay. Compared to the placebo, both ASA and captopril decreased mean PI values of both uterine arteries of all mares. On average, ASA decreased the PI of the uterine arteries by 25%; this was more ( P<0.05) than the average decrease (13%) caused by captopril. Both drugs decreased ( P<0.05) blood flow resistance in the ovarian arteries, although there was no difference ( P<0.05) in their efficacy. In addition, both ASA and captopril increased ( P<0.0001) plasma progesterone concentrations (18 and 17%, respectively). In conclusion, either ASA or captopril improved uterine and ovarian perfusion; however the effects on fertility were not determined.