Abstract
The effect of mild lipid extraction and phospholipases on isolated rat liver plasma membrane was investigated. Extraction of membrane at 4 ° with a shaked mixture of petrol ether- n-butanol resulted in a dramatic reduction of the concentration of phosphatidylethanolamine (−97%) and phosphatidylserine (−99%), whereas phosphatidylinositol was reduced to about 30% of the initial value. Simultaneously the activity of adenylate cyclase as well as that of Mg 2+-ATPase was strongly reduced −83 and −85%, respectively); another membrane enzyme, 5′-nucleotidase was slightly stimulated. The activity of solvent-treated adenylate cyclase was partially restored by addition of total membrane phospholipids or phosphatidylinositol, while phosphatidylserine was ineffective. Both phospholipase A and C reduced adenylate cyclase activity. However the effect of phospholipase C was prevented by serum albumin, while that of phospholipase A was not. This suggests that the effect of the latter enzyme may be related to alterations of phospholipids and (or) of membrane structure.
Published Version
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