Caprine cardiac sarcoplasmic reticulum: Effect of simulated ischemia on membrane structure and Ca(2+)-ATPase activity.

The sarcoplasmic reticulum was isolated and characterized in the pure form from normal caprine (Capra hircus) hearts. Under ischemic condition, fatty acids like palmitic acid, palmitoyl carnitine and oleic acid accumulatein vivo. These are known to have a detrimental effect on membrane components. The effects of simulated ischemia on the Ca(2+)-ATPase were studied using these fatty acidsin vitro at concentrations at which they occurin vivo in the ischemic heart. All three fatty acids inhibited Ca(2+)-ATPase activity. At lower concentrations, palmitoyl carnitine was the most potent, followed by oleic acid while palmitic acid displayed the least potency. Electron microscopy studies with fatty acids showed morphological disruptions in SR vesicles. The decline in Ca(2+)-ATPase activity could be attributed to the change in membrane morphology.