Histological Study of Bovine Corpora Lutea

Abstract

Corpora lutea removed at various times during the estrous cycle were studied after no treatment, treatment with oxytocin, oxytocin and HCG, oxytocin and bovine LH, and with HCG alone. These studies supported a hypothesis that luteal cells are derived from both granulosa and theca layers of the follicle. The granulosa- derived luteal cells develop into functioning luteal cells by about Day 4 of the estrous cycle, after which they undergo no further divisions. Therefore, granulosa-derived cells have limited potential. However, the smaller luteal cells derived from the theca interna respond to plasma luteotropin, multiply and grow into large luteal cells. These are mainly responsible for growth of the corpus luteum following Day 4. There was luteinization of the theca interna and granulosa layers of the follicles shortly before ovulation and in anovulatory (cystic) follicles. The collapse of the follicle and growth of the corpus luteum were described, with special emphasis on the patterns of mitotic activity before and after stimulation with exogenous luteotropin and on progesterone concentrations and contents. Growth and degeneration of a luteal cell were described.