Gonadotropin-releasing hormone stimulation of pituitary gonadotrope cells produces an increase in intracellular calcium

• Published in: Biology of reproduction Vol. 32; no. 2; pp. 269 - 278
• Main Authors: CLAPPER, D. L, CONN, P. M
• Format: Journal Article
• Language: English
• Published: Madison, WI Society for the Study of Reproduction 01.03.1985
• Subjects: Aminoquinolines - pharmacology; Animals; Biological and medical sciences; Calcimycin - pharmacology; calcium; Calcium - metabolism; Cell Separation; Female; Fluorescent Antibody Technique; Fundamental and applied biological sciences. Psychology; Gonadotropin-Releasing Hormone - analogs & derivatives; Gonadotropin-Releasing Hormone - antagonists & inhibitors; Gonadotropin-Releasing Hormone - pharmacology; Hormones and neuropeptides. Regulation; Hypothalamus. Hypophysis. Epiphysis. Urophysis; luteinizing hormone; Luteinizing Hormone - metabolism; luteinizing hormone-releasing hormone; pituitary (anterior); Pituitary Gland - cytology; Pituitary Gland - drug effects; Rats; Rats, Inbred Strains; Vertebrates: endocrinology; Calcium; Peptide hormone; Gonadotropin RH; Stimulation; Inorganic element; Vertebrata; Mammalia; Gonadotropic cell; Pituitary gland; Artiodactyla; Beef; Intracellular; Ungulata
• ISSN: 0006-3363; 1529-7268
• DOI: 10.1095/biolreprod32.2.269

Gonadotropin-releasing hormone (GnRH) stimulates pituitary gonadotrope cells to release luteinizing hormone (LH). Previous studies have indicated a role for Ca+2 in this process; however, the present study provides the first measurements of an increased intracellular Ca+2 concentration. Pituitary cell cultures enriched for gonadotropes were loaded with quin 2, a fluorescent Ca+2-sensitive molecule. Subsequent addition of GnRH to these cells produced a rapid (within 10 sec) increase in fluorescence (indicating an increase in intracellular free Ca+2). In contrast, two GnRH analogs, des1 GnRH (a very low-affinity binder to the GnRH receptor) and Ac[D-pCl-Phe1,2] DTrp3 DLys6 DAla10-GnRH (a pure GnRH antagonist) produced no such Ca+2 change, thus showing a correlation between increased intracellular Ca+2 and LH release. A functional relationship between increased Ca+2 and LH release was suggested by experiments in which LH release was inhibited from cells loaded with high levels of intracellular quin 2 (in order to chelate intracellular Ca+2). Since this inhibition was completely reversed by addition of the Ca+2 ionophore A23187, quin 2 was not toxic at the concentrations used and apparently inhibited LH release by buffering intracellular Ca+2. The results presented here are consistent with the hypothesis that GnRH-stimulated LH release is mediated by increased intracellular Ca+2 and support the notion that the rate-limiting step in GnRH-stimulated LH release is distal to Ca+2 mobilization.