Relationship between stimulated phosphatidic acid production and inositol lipid hydrolysis in intestinal longitudinal smooth muscle from guinea pig.
Accumulation of [32P]phosphatidic acid (PA) and total [3H]inositol phosphates (IPs) was measured in the longitudinal smooth-muscle layer from guinea-pig small intestine. Stimulation with carbachol, histamine and substance P produced increases in accumulation of both [3H]IPs and [32P]PA over the same concentration range. The increase in [32P]PA accumulation in response to carbachol (1 microM-0.1 mM) was inhibited in the presence of atropine (0.5 microM). Buffering the external free [Ca2+] to 10 nM did not prevent the carbachol-stimulated increase in [32P]PA accumulation. Carbachol and Ca2+ appear to act synergistically to increase accumulation of [32P]PA. In contrast, although incubation with noradrenaline also increased accumulation of [3H]IPs, no increase in accumulation of [32P]PA could be detected. These results suggest that an increase in formation of IPs is not necessarily accompanied by an increase in PA formation, and imply the existence of receptor-modulated pathways regulating PA concentrations other than by phospholipase-C-catalysed inositol phospholipid hydrolysis.
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002217:Carbachol / Q000494:pharmacology; D005260:Female; D006168:Guinea Pigs; D006632:Histamine / Q000494:pharmacology; D006868:Hydrolysis; D066298:In Vitro Techniques; D007295:Inositol Phosphates / Q000378:metabolism*; D008297:Male; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism*; D010712:Phosphatidic Acids / Q000378:metabolism*; D013373:Substance P / Q000494:pharmacology; D013403:Sugar Phosphates / Q000378:metabolism*
D007295:Inositol Phosphates; D010712:Phosphatidic Acids; D013403:Sugar Phosphates; D013373:Substance P; D006632:Histamine; D002217:Carbachol; D002118:Calcium