Potential leukocyte attractants in the bovine peri-ovulatory ovary

This study investigated interrelationships between the bovine ovarian cycle and white blood cells and tested the hypothesis that the ovary produces collagen-like materials with leukocyte attractant activity. We examined the in vitro secretion of leukocyte attractant activity by peri-ovulatory ovarian tissues and evaluated the leukocyte attractant potential of some ovarian biochemicals. Fluid from mature ovarian follicles and medium conditioned by follicular tissue, early luteal tissue or granulosa cells had significant attractant activity. The activity could be removed by protein precipitation but not by collagenase. Collagenase also failed to alter the electrophoretic profile of the samples. Collagenase (800 IU/ml), ascorbic acid (10-1,000 micrograms/ml) and CaCl2 (50-560 micrograms/ml) had significant leukocyte attractant effects. Native collagen types I and IV (100-1,000 micrograms/ml) had fewer expressed attractant activities, which were unaffected by collagenase pre-treatment. The attractant activity of collagenase itself was removed by protein precipitation. Our observations suggest: (1) that follicular and luteal tissues produce leukocyte attractant(s); (2) that granulosa cells contribute to the secretion of this material; (3) that the principal ovarian attractants are neither the native collagen types I or IV nor their collagenase-releasable fragments; and (4) that collagenase, ascorbic acid and Ca2+ are strong candidates as attractant constituents of ovarian secretions.