Stimulation of phospholipid metabolism in embryonic muscle cells treated with phospholipase C.

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Abstract
Phospholipid metabolism is dramatically stimulated in cultured myogenic embryonic chicken cells where cell fusion was inhibited with phospholipase C (phosphatidylcholine cholinephosphohydrolase; EC 3.1.4.3). Phospholipase C was active under the culture conditions as shown by the degradation of exogenous phosphatidylcholine. Rates of incorporation of 32Pi and [methyl-3H]choline into lipids were .apprx. 5-fold greater in phospholipase-treated cells than in either untreated fusing cells or untreated cells prevented from fusing by Ca deprivation. The greatest stimulation in the phospholipase C-treated cultures occurred with synthesis of phosphatidylcholine and sphingomyelin. Synthesis of phosphatidylinositol and cardiolipin was not stimulated. Degradation of cellular [32P]phosphatidylcholine and appearance in the culture medium of the degradation product [32P]phosphocholine were both increased. Levels of total cellular phospholipids and of individual phospholipid classes were similar in control and phospholipase-treated cells. The membrane phospholipid composition in myogenic cells is evidently controlled by a regulatory mechanism which increases the synthesis of phospholipids that are degraded in the presence of the phospholipase.