Characterization of voltage-sensitive calcium channels in a clonal pituitary cell line |
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Authors: | G A Shangold S Kongsamut R J Miller |
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Affiliation: | 1. Department of Obstetrics and Gynecology, Chicago, Illinois 60637, USA;2. Department of Pharmacological and Physiological Sciences University of Chicago Pritzker School of Medicine Chicago, Illinois, 60637, USA |
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Abstract: | We have pharmacologically characterized voltage sensitive calcium channels (VSCCs) in GH3 cells, an anterior pituitary clonal cell line known to secrete prolactin and growth hormone. Raising the medium K+ concentration from 5 to 50 mM caused an immediate increase in net 45Ca2+ uptake which remained apparent over a 15 minute time course. 45Ca2+ uptake was maximally stimulated nearly 10-fold over basal levels. This K+-induced stimulation of Ca2+ uptake was not prevented by 10-5M tetrodotoxin or by replacing sodium with choline in the assay medium. Ca2+ uptake was, however, inhibited by several VSCC antagonists: nitrendipine, D-600, diltiazem and Cd2+. Further, the novel dihydropyridine VSCC agonists, BAY K8644 and CGP 28392, enhanced 50 mM K+-stimulated 45Ca2+ uptake and these effects were blocked by nitrendipine. |
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