INFLUENCE OF ESTROGEN ON ANTIBACTERIAL AND IMMUNOGLOBULIN SECRETORY ACTIVITIES OF UTERINE FLUIDS FROM OVARIECTOMIZED MARES

Effect of estrogen (E2) and progesterone (P4) on uterine antibacterial activity and immunoglobulin concentrations in mares was studied. In 2 in vitro experiments, 6 mixed-breed mares were ovariectomized, and ut erine fluid and blood serum were analyzed. Antibacterial assay methods were used to determine inhibitory effects on Streptococcus zooepidemi cus of uterine fluid samples collected on days 3, 5, and 8, and serum obtained on day 8 of treatment. Single radial immunodiffusion methods were used to quantify amounts of IgA and IgG in uterine fluid and seru m on days 3, 5, 8, and 14 of treatment. Neither E2 nor P4 increased ac tivity of serum and uterine fluid against S zooepidemicus. Numbers of colony-forming units per milliliter of bacteria were significantly (P < 0.01) lower in control Hanks' balanced salt solution with 1.0% gelat in (HBSSG) than in uterine fluids. Bacterial numbers were significantl y (50%) greater in uterine fluids and serum than in HBSSG controls for both treatments. Both fluids, especially serum, supported significant ly (P < 0.01) more growth of S zooepidemicus than did HBSSG when incub ated for 0, 2, and 4 hours. These findings are in contrast to previous reports of antibacterial activity in the uterus of sexually intact ma res undergoing an estrous cycle: great reduction of bacterial count in uterine fluid from mares in diestrus, and significant increases in ba cterial numbers in uterine fluid or serum from mares in estrus. Treatm ent comparisons between serum and uterine fluid IgA. and IgG concentra tions were not significantly different, although overall IgA concentra tion in the uterus was higher than concentration in serum. The IgG con centration in uterine fluid was higher in P4- than E2-treated mares. H owever, IgG concentration was significantly (P < 0.01) higher in uteri ne fluid on day 8 in P4-treated mares than on day 3 or 5. Results of t his study indicate that neither immunoglobulin concentration nor hormo ne treatment has a direct effect on streptocidal activity.