title: Inhibition of the adrenal chromaffin cell membrane calcium pump by caffeine and various divalent cations.
abstract: Caffeine, 50 mM, inhibited ATP-mediated 45Ca uptake by plasma membrane vesicles from bovine adrenal medullary microsomes by 40 percent. Hg++ (0.09 mM) completely inhibited 45Ca uptake, while Cd++ (0.3 mM) and Ba++ (0.3 mM) produced mean depressions of 80 and 41 percent, respectively. 45Ca uptake in the presence of Zn++ (0.3mM) was not significantly different from controls. Inhibition of calcium accumulation in plasma membrane vesicles by these agents was not correlated with their ability to inhibit the enzyme Ca++-ATPase. Caffeine and certain divalent cations may modify secretory responses by inhibiting the active extrusion of calcium through the adrenal medullary plasma membrane.
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000313:Adrenal Medulla / Q000166:cytology*; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D002110:Caffeine / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D002132:Calcium Radioisotopes; D002395:Catecholamines / Q000378:metabolism; D002417:Cattle; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D002838:Chromaffin System / Q000166:cytology*; D066298:In Vitro Techniques; D008670:Metals / Q000494:pharmacology*
chemical_list: D002132:Calcium Radioisotopes; D002395:Catecholamines; D008670:Metals; D002110:Caffeine; D000251:Adenosine Triphosphatases; D002118:Calcium