The sarcolemmal Ca2+-ATPase of the ischemic-reperfused myocardium: protective effect of hypocalcemia on calmodulin-stimulated activity

Life Sci. 1998;62(1):29-36. doi: 10.1016/s0024-3205(97)01035-7.

Abstract

This study was designed to examine the role of calcium in the ischemia-induced changes of calmodulin-stimulated Ca2+-ATPase activity of heart sarcolemma of dogs subjected to coronary artery ligation (90 min) and reperfusion (30 min). This was attained by the application of systemic hemodialysis with low Ca2+ dialysate in six dogs (group A) and the comparison of the results with those obtained from animals subjected to normal Ca2+ hemodialysis (control group B, n=7). A very significant (p<0.001) decrease was found in the calmodulin-stimulated Ca2+-ATPase activity measured in the ischemic and non-ischemic parts of group B. This was associated with a decrease in the maximal velocity (v(max)) of the reaction of stimulation and an increase in the apparent Km for calmodulin. The kinetics of the calmodulin-stimulated Ca2+-ATPase also assessed in the presence of trifluoroperazine, a specific inhibitor for calmodulin binding, showed that the affinity for calmodulin was higher in the ischemic part of group A than of B, while v(max) was not substantially different. The above data may suggest that the inhibition of the calmodulin-stimulated Ca2+-ATPase produced by ischemia-reperfusion and its preservation under low Ca2+, are exerted at the calmodulin-binding site of the enzyme.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calcium-Transporting ATPases / drug effects*
  • Calcium-Transporting ATPases / metabolism
  • Calmodulin / metabolism
  • Calmodulin / pharmacology*
  • Dogs
  • Female
  • Heart / drug effects*
  • Hypocalcemia / physiopathology*
  • Male
  • Myocardial Ischemia / metabolism
  • Myocardial Reperfusion
  • Myocardium / enzymology
  • Sarcolemma / drug effects
  • Sarcolemma / enzymology*

Substances

  • Calmodulin
  • Calcium-Transporting ATPases