Effect of estradiol and progesterone on antistaphylococcal activity of neutrophils from ovariectomized mares

Neutrophils isolated from jugular blood of ovariectomized mares were studied for the effect of estradiol and progesterone on bactericidal activity against Staphylococcus aureus. In experiment 1, neutrophils obtained from 4 mares were tested for bactericidal activity by adding estradiol (43 pg/ml) or progesterone (6.4 ng/ml) to the bactericidal assay. In experiment 2, 3 of the 4 ovariectomized mares were given 2 mg of estradiol, IM, daily for 3 days. Eighteen days after the initial estradiol injection, mares were given 300 mg of progesterone, IM, for 6 days. Neutrophils from these mares were tested for bactericidal activity 4 days after the initial estradiol injection, 17 days after the initial estradiol injection (control), and 7 days after the first progesterone injection. Bactericidal activity was measured at 30 and 120 minutes by counting the number of colony-forming units remaining. Neutrophil antistaphylococcal activity was not altered by adding estradiol and progesterone to the assay or by supplementing ovariectomized mares with estradiol and progesterone (P greater than 0.05).