Neutrophil migration into the uterine lumen of the cow: The influence of endogenous and exogenous sex steroid hormones using two intrauterine chemoattractants

Neutrophil migration into the uterine lumen in response to the intrauterine infusion of both an oyster glycogen suspension and a bacteria-free filtrate obtained after incubation of Actinomyces pyogenes in cooked meat medium was studied in 4 cows at estrus (Day 0) and at diestrus (Day 10). In addition, the same chemoattractants were used in 5 other cows following bilateral ovariectomy and after parenteral treatment with exogenous estradiol 17β and progesterone in oil. Large numbers of cells (average viability >85%, purity 95%) were obtained with both chemoattractants. In cyclic and bilaterally ovariectomized cows bacteria-free filtrate produced a greater migratory response than oyster glycogen, and the differences were significant (P < 0.01 and P < 0.002, respectively). On Day 10 of the estrous cycle a higher number of neutrophils was recovered than on Day 0 following infusion of oyster glycogen and bacteria-free filtrate, and again the differences were significant (P < 0.003 and P < 0.001, respectively). Following treatment of ovariectomized cows with estradiol and progesterone, greater response was observed for progesterone than for estradiol after oyster glycogen and bacteria-free filtrate treatment with significant differences (P < 0.002 and P < 0.003, respectively). Both chemoattractants produced adequate numbers of viable neutrophils suitable for subsequent evaluation of their function in vitro. The increased neutrophil response induced by progesterone, both in normal cyclic cows and after ovariectomy following progesterone treatment, may be a compensatory one due to reduced neutrophil phagocytosis and bactericidal activity or to the suppression of other uterine defense mechanisms, since this response is inconsistent with the long-recognized observation that the uterus of the cow is more susceptible to infection in diestrus than in estrus.