Endocrinology, Vol 126, 754-758, Copyright © 1990 by Endocrine Society

ARTICLES

Cytosolic Ca2+ in melanotrophs: pharmacological insights into regulatory influences of electrical activity and ion channels

EF Nemeth, PS Taraskevich and WW Douglas
Department of Physiology and Biophysics, Case Western Reserve University Cleveland, Ohio 44105.

The concentration of intracellular free Ca2+ ([Ca2+]i) was measured in melanotrophs, the characteristic endocrine cells of the pars intermedia of the rat pituitary gland, using the fluorescent Ca indicator fura-2. The resting [Ca2+]i was 211 +/- 8 nM and was little affected by tetrodotoxin (TTX; 5 or 10 microM), which inhibits the spontaneous action potentials that occur in these cells. Removal of extracellular Ca2+ (by chelation with EGTA) or addition of the Ca channel blocker nimodipine (1 microM) produced a rapid fall in [Ca2+]i, which occurred whether TTX was present or not. Excess K+ (60 mM), veratridine (10 or 100 microM) and BAY K 8644 (1 microM) each caused a rapid rise in [Ca2+]i, which was blocked or truncated by EGTA or nimodipine. TTX blocked or truncated the increases in [Ca2+]i induced by veratridine, but not those induced by either excess K+ or BAY K 8644. The results show that manipulations that increase or decrease hormone output increase or decrease [Ca2+]i. Furthermore, the resting [Ca2+]i appears to depend importantly on Ca influx, since it is rapidly and markedly reduced by removal of extracellular Ca2+ or addition of a Ca channel blocker.

This article has been cited by other articles:

				R. Webb, P. C. Garnsworthy, J.-G. Gong, and D. G. Armstrong Control of follicular growth: Local interactions and nutritional influences J Anim Sci, January 1, 2004; 82(13_suppl): E63 - 74. [Abstract] [Full Text] [PDF]

				K. Tanaka, I. Shibuya, N. Kabashima, Y. Ueta, and H. Yamashita Inhibition of Voltage-Dependent Calcium Channels by Prostaglandin E2 in Rat Melanotrophs Endocrinology, December 1, 1998; 139(12): 4801 - 4810. [Abstract] [Full Text] [PDF]