GRF elevates cytosolic free calcium concentration in rat anterior pituitary cells

• Published in: The American journal of physiology Vol. 253; no. 5 Pt 1; pp. E591 - E594
• Main Authors: Schöfl, C, Sandow, J, Knepel, W
• Format: Journal Article
• Language: English
• Published: United States 01-11-1987
• Subjects: 8-Bromo Cyclic Adenosine Monophosphate - pharmacology; Animals; Benzofurans; Calcium - metabolism; Cytosol - metabolism; Dinoprostone; Ethers - pharmacology; Fluorescent Dyes; Fura-2; Growth Hormone-Releasing Hormone - pharmacology; In Vitro Techniques; Ion Channels - drug effects; Ion Channels - metabolism; Ionomycin; Magnesium - pharmacology; Male; Nifedipine - pharmacology; Pituitary Gland, Anterior - drug effects; Pituitary Gland, Anterior - metabolism; Prostaglandins E - pharmacology; Rats; Rats, Inbred Strains; Spectrometry, Fluorescence
• ISSN: 0002-9513
• DOI: 10.1152/ajpendo.1987.253.5.E591

The effect of human growth hormone-releasing factor (GRF) on intracellular free calcium concentration ([Ca2+]i) was examined in rat anterior pituitary cells. The [Ca2+]i was monitored directly by means of the intracellularly trapped fluorescent indicator, fura-2. GRF rapidly elevated [Ca2+]i, reaching a new plateau within approximately 30 s. The half-maximally effective concentration of GRF was approximately 130 pM. GRF produced a maximal increase in [Ca2+]i by approximately 120 nM. The GRF (2 nM)-induced elevation of [Ca2+]i was abolished by removal of extracellular calcium (Ca2+ omitted, 2 mM EGTA). The GRF (2 nM)-caused rise in [Ca2+]i was largely reduced in the presence of the calcium channel blockers Mg2+ (31.2 mM) or nifedipine (1 microM). An increase in [Ca2+]i by approximately 60 nM was elicited by the addition of prostaglandin E2 (1 microM), which can stimulate growth hormone secretion independent of GRF receptors. These data indicate that GRF elevates the [Ca2+]i, possibly in somatotrophs; this GRF-induced increase in [Ca2+]i may depend on an influx of extracellular Ca2+, largely through Mg2+- and nifedipine-sensitive calcium channels.