AJP - Endocrinology and Metabolism, Vol 255, Issue 4 E488-E495, Copyright © 1988 by American Physiological Society

ARTICLES

Calcium response of single adrenal glomerulosa cells to external potassium

S. J. Quinn, G. H. Williams and D. L. Tillotson
Department of Physiology, Boston University School of Medicine 02118.

The cytosolic calcium (Cai2+) response to external potassium (K+) was examined in single rat zona glomerulosa (ZG) cells by monitoring fura-2-fluorescence with microspectrofluorometry and digital imaging microscopy. The majority (68%) of morphologically identified ZG cells demonstrated an increase in Cai2+ during K+ stimulation. Cai2+ rose monotonically from a mean basal level of 232 +/- 15 to 285 +/- 37 nM at 5 mM and 680 +/- 60 nM at 10 mM K+ for responsive ZG cells. The Cai2+ response was largely (greater than 90%) inhibited by nominal zero calcium or 1 mM cadmium and substantially modified in the presence of 10(-5) M nifedipine. The response kinetics were characterized by a rising phase that depended on the size of the Cai2+ change, with larger increases associated with a faster onset. Cai2+ approached a plateau level that was sustained for the duration of K+ stimulation from 1 to 5 min. Cai2+ appeared to be more uniformly distributed across the cell under resting conditions than during stimulation. Assessment of the Cai2+ response in single ZG cells documents 1) a majority, but not all, of ZG cells respond to K+, 2) simple kinetics consisting of a rapid onset and sustained plateau Cai2+ level, 3) a dose-dependent Cai2+ increase in the physiological range of K+, and 4) inhibition by calcium channel blockers and sensitivity to small increases in K+ consistent with activation of low-threshold calcium channels.

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