Molecular Pharmacology, Vol 6, 407-415, Copyright © 1970 by the American Society for Pharmacology and Experimental Therapeutics

The Role of Adenosine Triphosphate and Adenosine Triphosphatase in the Release of Catecholamines from the Adrenal Medulla

IV. Adenosine Triphosphate-Activated Uptake of Calcium by Microsomes and Mitochondria

¹ Department of Pharmacology, University of Kansas Medical Center, Kansas City, Kansas 66103

Studies were carried out on radioactive calcium uptake by cell fractions isolated from bovine adrenal medullae. Microsomes showed an active uptake of calcium which was dependent on ATP and Mg⁺⁺, potentiated by an ATP-generating system, and inhibited by agents known to block calcium uptake by muscle microsomes. Mitochondria showed an ATP-activated uptake of calcium which was inhibited by azide, oligomycin, on 2,4-dinitrophenol. These agents did not inhibit active uptake by the microsomes. A semipurified chromaffin granule preparation also showed ATP-activated calcium uptake, but it was largely inhibited by azide. Thiocyanate, which reduced calcium uptake by the microsomes, caused the release of catecholamines from perfused adrenal glands. The regulation of intracellular calcium by the adrenal medulla and its influence on catecholamine secretion are discussed, with emphasis on similarities to muscle physiology.

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ACKNOWLEDGMENTS We wish to acknowledge the technical assistance of Mr. J. L. Alderman, Mr. J. Bernstein, and Mr. D. W. Friesen.