Development of antral follicles in cattle after prostaglandin-induced luteolysis: changes in serum hormones, steroids in follicular fluid, and gonadotropin receptors.
Changes in growth, concentrations of steroids in follicular fluid, and numbers of gonadotropin receptors in follicles 6 mm or more in diameter were examined 12, 24, 36, 48, 60, and 72 h after prostaglandin (PG)-induced luteolysis in heifers. Follicles with higher concentrations of estradiol than progesterone and androgens in follicular fluid (FF) were classified as estrogen active (E-A). Follicles with higher concentrations of progesterone or androgens than estradiol in follicular fluid were classified as estrogen inactive (E-I). Although E-A and E-I follicles were similar in size 12-72 h after PG treatment, before the preovulatory surge of LH, numbers of granulosa cells, estradiol concentrations, and capacities of follicles to specifically bind gonadotropins were markedly lower in E-I follicles. Most E-I follicles had histological signs of atresia, whereas E-A follicles did not. Sizes, concentrations of steroids in FF, and specific binding of gonadotropins to follicle cells did not change in E-A or E-I follicles 12-72 h after PG treatment but before the preovulatory surge of LH. However, diameters of E-A follicles were highly correlated with concentrations of estradiol and progesterone in FF and with capacities of granulosa and thecal cells to specifically bind [125I] iodo-hCG. In contrast, diameters of E-A follicles were highly negatively correlated with concentrations of testosterone in FF and with capacities of granulosa cells to specifically bind [125I] iodobovine FSH. We conclude that E-I follicles are atretic and E-A follicles are potentially ovulatory follicles. In addition, after a single injection of PG during an estrous cycle in heifers, the growth the differentiation of ovulatory follicles were not synchronized.
D000818:Animals; D002417:Cattle / Q000502:physiology*; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood; D006728:Hormones / Q000097:blood*; D007986:Luteinizing Hormone / Q000097:blood; D006080:Ovarian Follicle / Q000187:drug effects*; D011374:Progesterone / Q000097:blood; D011453:Prostaglandins / Q000494:pharmacology*; D011956:Receptors, Cell Surface / Q000378:metabolism*; D011962:Receptors, FSH; D011974:Receptors, LH; D013256:Steroids / Q000032:analysis*
D006728:Hormones; D011453:Prostaglandins; D011956:Receptors, Cell Surface; D011962:Receptors, FSH; D011974:Receptors, LH; D013256:Steroids; D011374:Progesterone; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone