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  • Title: Further studies on the influence of GnRH on the biosynthesis of gonadotropins in female frogs (Rana pipiens).
    Author: Stamper DL, Licht P.
    Journal: Gen Comp Endocrinol; 1993 Oct; 92(1):104-12. PubMed ID: 8262352.
    Abstract:
    To further investigate the action of gonadotropin-releasing hormone (GnRH) on pituitaries of female frogs (Rana pipiens), gonadotropin (Gth) secretion and synthesis was measured following either the in vivo or in vitro exposure to GnRH. Treating frogs with a GnRH-agonist (GnRHa) in vivo for either 2 or 5 days led to an elevation in plasma Gth compared to that of saline-injected controls. In general, the pattern of Gth secretion in vitro paralleled changes observed in their plasma levels. GnRHa-treated frogs also had depressed pituitary content of Gth as compared to controls. Pituitaries from frogs treated with GnRHa for 5 days had higher levels of Gth synthesis than those of controls; however Gth synthesis in females treated with GnRHa for only 2 days was not elevated. After 30 hr of continuous exposure to 100 ng/ml GnRH in vitro, glands from females secreted markedly higher levels of LN and FSH than glands not exposed to the secretagogue. The levels of LH and FSH contained within pituitaries exposed to GnRH were significantly less than those of control glands. Prolonged exposure to GnRH elevated both the secretion of radiolabeled Gth as well as increased the total synthesis of Gth (compared to those of controls). These results indicate that GnRH can stimulate the biosynthesis of Gth in pituitaries of female frogs; however these results differ from those previously obtained with males. It appears that female glands require a much longer duration of GnRH stimulation than males before Gth synthesis is elevated.
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