Cadmium effect on the Na,K-ATPase system in cultured vascular smooth muscle cells.
The present study focuses on the interaction between cadmium (Cd) and the Na, K-ATPase system in in vitro grown vascular smooth muscle cells (VSMCs) derived from the rat carotid artery. In disrupted VSMCs rendered permeable by osmotic shock, Cd inhibited Na, K-ATPase; I50 was reached at 10(-5) M Cd. Mg-ATPase was also inhibited by Cd; I50 was attained at concentrations of 10(-4) M Cd. Cd inhibition of Na,K-ATPase in the VSMCs was noncompetitive with respect to Na, K, and ATP. Rubidium transport experiments performed with intact VSMCs demonstrated that within an incubation period of 150 minutes, a concentration of 10(-4) M Cd in the extracellular fluid exerted no acute effect on the Na-K pump. Within this time interval, intracellular Cd attained a concentration eightfold higher than the extracellular Cd concentration. Thus, it appears that under acute conditions Cd exerts its inhibitory effect on Na, K-ATPase only in disrupted VSMCs. The data further suggest that, in the VSMC, conditions under which Cd inhibits Na, K-ATPase are consistent with inhibition from the cytoplasmic side of the cell membrane.
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D017301:Ca(2+) Mg(2+)-ATPase; D002104:Cadmium / Q000378:metabolism / Q000494:pharmacology*; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D002339:Carotid Arteries; D002478:Cells, Cultured; D004492:Edetic Acid / Q000494:pharmacology; D007700:Kinetics; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000201:enzymology* / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D012413:Rubidium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors / Q000378:metabolism*
D002104:Cadmium; D004492:Edetic Acid; D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases; D000254:Sodium-Potassium-Exchanging ATPase; D012413:Rubidium