PHOSPHOLIPASE-C BETA-2 IN VASCULAR SMOOTH-MUSCLE

Receptor-mediated inositol 1,4,5-trisphosphate formation in most tissu es is dependent on a variety of phospholipase C isoforms. To determine wh ich phospholipase C isoforms were present in vascular smooth muscl e compared to brain, liver, and spleen, we extracted proteins from the se tissues and separated and identified the phospholipase C isoforms b y immunoblotting. Aliquots of rat tail artery were examined by this pr ocedure, together with aliquots of rat liver, spleen, cerebral cortex, hippocampus, cerebellum, aorta, and mesenteric artery. Phospholipase C gamma 1 was shown to be present in all of these tissues, while phosp holipase C beta 1 was shown to be limited to fractions from brain. Pho spholipase C delta 1 was detected in rat tail artery, mesenteric arter y, aorta, and brain. Phospholipase C beta 2 was found in rat tail arte ry, liver, and brain. This is the first report of phospholipase C beta 2 in tissues other than HL60 cells. Since G proteins activate IP3 pro duction via stimulation of phospholipase C beta isoforms in many tissu es, and agonist-stimulated IP3 production in smooth muscle requires G protein activation, phospholipase C beta 2 may be required for agonist -stimulated force production in vascular smooth muscle. (C) 1996 Wiley -Liss, Inc.