Differential sensitivity of canine cardiac sarcolemmal and microsomal enzymes to inhibition by free radical-induced lipid peroxidation.
Sarcolemmal and microsomal membranes prepared from adult canine cardiac myocytes (sarcolemmal Na+, K+-ATPase = 71.8 mumol/mg per hr and microsomal rotenone-insensitive NADH cytochrome c reductase = 114 mumol/mg per hr) were each preincubated at 37 degrees C in the presence of a free radical generating system consisting of dihydroxyfumarate and Fe -ADP; loss of the Na+, K+-ATPase and reductase activities, as well as the associated increases in lipid peroxidation, measured by malondialdehyde formation, were temporally correlated in both systems. The ATPase was inhibited 70% when the malondialdehyde was 71 nmol/mg protein at 20 minutes and 90% when malondialdehyde was 138 nmol/mg protein at 90 minutes. Inhibition of reductase activity occurred more gradually, displaying a 27% loss of activity when malondialdehyde reached 34 nmol/mg protein at 20 minutes and 60% with a malondialdehyde value of 67 nmol/mg protein at 90 minutes. The greater susceptibility of the sarcolemma to free radical-induced membrane damage may be due to the higher content of unsaturated fatty acids in this membrane, compared to microsomes.
D000818:Animals; D004285:Dogs; D005609:Free Radicals; D008054:Lipid Peroxides / Q000378:metabolism; D008315:Malondialdehyde / Q000032:analysis; D008861:Microsomes / Q000201:enzymology*; D009206:Myocardium / Q000201:enzymology / Q000648:ultrastructure*; D010088:Oxidoreductases / Q000037:antagonists & inhibitors; D012508:Sarcolemma / Q000201:enzymology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors
D005609:Free Radicals; D008054:Lipid Peroxides; D008315:Malondialdehyde; D010088:Oxidoreductases; D000254:Sodium-Potassium-Exchanging ATPase