Membrane phospholipid metabolism of rat myocardial cells during hypothermia and rewarming.

The phospholipid bilayer of the plasma membrane plays an important role in forming a functional barrier against leakage of ions and other cell constituents. We have examined the effect of an exogenously added phospholipase C (PLC) on phospholipid degradation in isolated rat myocardial cells subjected to hypothermia (5 degrees C) and hypothermia followed by rewarming to 37 degrees C. The activity of PLC was measured as glycerol output to the incubation medium since the combined action of PLC and endogenous lipases will result in glycerol production. Addition of PLC resulted in a significantly higher output of glycerol in rewarmed myocytes than in myocytes kept constantly at 5 degrees C and 37 degrees C. Rewarmed cells also showed the highest leakage of lactate dehydrogenase (LDH), but there was no additional effect of PLC on LDH leakage. Normal levels of cellular ATP were maintained in all myocyte groups. These results show that rewarming from hypothermia may cause structural derangements in the phospholipid bilayer of the sarcolemma which in turn could favor attack by endogenous phospholipases.