Follicle-stimulating hormone enhances the development of preantral follicles in juvenile rats

• Published in: Biology of reproduction Vol. 57; no. 5; pp. 990 - 998
• Main Authors: MCGEE, E. A, PERLAS, E, LAPOLT, P. S, TSAFRIRI, A, HSUEH, A. J. W
• Format: Journal Article
• Language: English
• Published: Madison, WI Society for the Study of Reproduction 01.11.1997
• Subjects: Animals; Animals, Newborn; Biological and medical sciences; Blotting, Western; Chorionic Gonadotropin - metabolism; Female; Follicle Stimulating Hormone - pharmacology; Fundamental and applied biological sciences. Psychology; Hormone metabolism and regulation; Hypophysectomy; Inhibins - immunology; Inhibins - metabolism; Luteinizing Hormone - metabolism; Mammalian female genital system; Organ Size - drug effects; Ovarian Follicle - drug effects; Ovarian Follicle - growth & development; Ovary - drug effects; Ovary - growth & development; Rats; Rats, Sprague-Dawley; Receptors, LHRH - antagonists & inhibitors; Vertebrates: reproduction; Rat; Rodentia; Gonadotropin RH; Gonadotropin; HCG; Placental hormone; Young animal; Hypothalamic hormone; Ovary; Vertebrata; Mammalia; Adenohypophyseal hormone; Female genital system; FSH; Hormone releasing factor; Ovarian follicle
• ISSN: 0006-3363; 1529-7268
• DOI: 10.1095/biolreprod57.5.990

The stimulatory effects of gonadotropins on antral and preovulatory follicles are well known, but conflicting results have been reported regarding the gonadotropin responsiveness and dependency of preantral follicles. Taking advantage of the relatively uniform development of the first wave of follicles in the postnatal rat ovary, we evaluated the role of endogenous and exogenous gonadotropins on preantral follicle development. Reduction of the high levels of gonadotropins present in juvenile rats by either hypophysectomy (at Day 15) or GnRH antagonist treatment (starting from Day 11 of age) resulted in decreased ovarian weight at Day 19 of age that was associated with a reduced number of developing follicles and increased atresia of remaining follicles. In contrast, treatment with FSHctp (a long-acting FSH agonist) in intact (Days 5-19 of age), hypophysectomized (Days 15-19), or GnRH antagonist-treated (Days 11-19) animals resulted in increased ovarian weight and follicle development as determined histologically and by inhibin-alpha expression. A dose-dependent stimulatory effect of hCG on ovarian weight was seen when animals were cotreated with FSHctp and the GnRH antagonist. At low doses of hCG, augmentation of antral follicle formation occurred, whereas higher doses of hCG led to morphological signs of luteinization. These findings demonstrate the important role of endogenous gonadotropins in preantral follicle development and indicate that preantral follicles are highly responsive to exogenous gonadotropins.