Phosphodiesteratic breakdown of endogenous polyphosphoinositides in nerve ending membranes.
When a membrane preparation, obtained by freezing and thawing nerve endings labeled by preincubation with 32pi, is incubated in the presence of millimolar Ca2+, there is a rapid and selective loss of label from the polyphosphoinositides and a concomitant increase in labeled inositol di- and triphosphates recovered. When the membranes are not prelabeled and are exposed to [gamma-32P]ATP under similar conditions, phosphatidate labeling is enhanced, indicating increased availability of diacylglycerol. These observations provide evidence for the presence of membrane-bound, Ca2+-stimulated phosphodiesterase activity (phospholipase C) acting on endogenous polyphosphoinositides. The implications of these findings are discussed in respect to the "phosphatidylinositol" cycle.
D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D002462:Cell Membrane / Q000201:enzymology; D002540:Cerebral Cortex / Q000201:enzymology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D009411:Nerve Endings / Q000201:enzymology*; D010716:Phosphatidylinositols / Q000378:metabolism*; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism*; D010738:Type C Phospholipases / Q000378:metabolism
D010716:Phosphatidylinositols; D010727:Phosphoric Diester Hydrolases; D010738:Type C Phospholipases; D002118:Calcium