Production of lysophospholipids and free fatty acids by a sarcolemmal fraction from canine myocardium.

The potential for injury of myocardial sarcolemma by endogenous lipases was studied. The sarcolemmal fraction was incubated for 30 min under conditions found optimal for hydrolysis of exogenous phosphatidylethanolamine (5 mM calcium, pH 7.0, 37°C). Incubation of the sarcolemmal fraction increased significantly the level of total free fatty acids (14.1 to 31.1 nmoles/mg protein, P < 0.001); in addition, production of arachidonic acid was increased significantly (P < 0.01). Lysophosphatidylcholine was increased significantly (P < 0.01) but the content of lysophosphatidylethanolamine was unchanged. A large proportion of the above free fatty acids (10.2 nmoles/mg protein) was derived from the hydrolysis of triacylglycerols. These data demonstrate that the sarcolemmal fraction preferentially hydrolyses endogenous membrane phosphatidylcholine at neutral pH in the presence of calcium with the formation of lysophosphatidylcholine and free fatty acids including arachidonic acid.