Influence of calcium antagonists on heart sarcolemmal (Na+ + K(+)-ATPase.
The effect of calcium entry blocking agents nitrendipine and flunarizine on Mg(2+)-ATPase, (Mg2+ + Na(+)-ATPase, (Na+ + K(+)-ATPase and (Mg2+ + Ca(2+)-ATPase activities was studied. Nitrendipine (1 mumol/l-1) exerted a stimulatory effect on (Mg2+ + Na(+)-ATPase activity. Kinetic analysis of this effect revealed a two-fold rise in Vmax value and lowered Km value for activation of the enzyme by Na+ ions. In concentrations 10(-7) and 10(-5) mol.l-1 flunarizine behaved as a non-specific inhibitor of all sarcolemmal ATPases investigated. Nevertheless, in concentration of 10(-6) mol.l-1 flunarizine inhibited selectively the (Mg2+ + Na(+)-ATPase and (Na+ + K(+)-ATPase activities of myocardial sarcolemma. These observations provided evidence that both flunarizine and nitrendipine, in the concentration 10(-6) mol.l-1, modulate the (Mg2+ + Na(+)-ATPase and (Na+ + K(+)-ATPase activities in cardiac sarcolemma. These side effects of the above drugs particularly that of nitrendipine might have potential physiological relevance.
Dzurba
A
A
Institute for Heart Research, Slovak Academy of Sciences, Bratislava, CSFR.
Breier
A
A
Slezák
J
J
Stankovicová
T
T
Vrbjar
N
N
Ziegelhöffer
A
A
D000251:Adenosine Triphosphatases; D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D005444:Flunarizine / Q000494:pharmacology; D009206:Myocardium / Q000201:enzymology* / Q000648:ultrastructure; D009568:Nitrendipine / Q000494:pharmacology; D051381:Rats; D012508:Sarcolemma / Q000201:enzymology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
D002121:Calcium Channel Blockers; D009568:Nitrendipine; D000251:Adenosine Triphosphatases; D017301:Ca(2+) Mg(2+)-ATPase; C035123:magnesium sodium ATPase; D000252:Calcium-Transporting ATPases; D000254:Sodium-Potassium-Exchanging ATPase; D005444:Flunarizine