title: Inhibition of nitric oxide synthase activity in dispersed gastric muscle cells by protein kinase C.
abstract: The present study examined whether NO synthase (NOS) activity in gastric muscle cells was inhibited by protein kinase C (PKC). Vasoactive intestinal peptide (VIP) increased L-[3H]citrulline production (a coproduct and index of NO synthesis) in muscle strips (81.9 +/- 11.6%) and dispersed muscle cells (80.9 +/- 4.6%) of rabbit stomach. Cholecystokinin octapeptide (CCK-8), carbachol, and phorbol 12-myristate 13-acetate (PMA) inhibited VIP-induced L-[3H]citrulline production in muscle cells and muscle strips; the inhibition was reversed by pretreatment with the PKC inhibitor, calphostin C. The Ca(2+)-mobilizing agents, CCK-8, acetylcholine, ionomycin, and KCl, all of which increased PKC activity in dispersed muscle cells, did not increase L-[3H]citrulline production. After treatment of the cells with calphostin C, all four agents stimulated L-[3H]citrulline production, although to a lesser extent than VIP (approximately 50%). VIP-induced relaxation of basal but not carbachol-stimulated tension was accompanied by increase in L-[3H]citrulline production and was inhibited by the NOS inhibitor NG-nitro-L-arginine (L-NNA). Preincubation of carbachol-treated muscle strips with calphostin C restored the ability of VIP to stimulate L-[3H]citrulline production and the ability of L-NNA to inhibit VIP-induced relaxation. We conclude that 1) VIP-stimulated NOS activity is inhibited by agents that increase PKC activity in gastric smooth muscle cells, and 2) agents that increase both cytosolic free Ca2+ concentration and PKC activity stimulate NOS activity only when PKC activity is suppressed.
authors.affiliation: Department of Physiology, Medical College of Virginia, Richmond 23298-0711.
authors.forename: K S
authors.initials: KS
authors.lastname: Murthy
authors.forename: J G
authors.initials: JG
authors.lastname: Jin
authors.forename: G M
authors.initials: GM
authors.lastname: Makhlouf
mesh_terms: D000594:Amino Acid Oxidoreductases / Q000037:antagonists & inhibitors*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002956:Citrulline / Q000096:biosynthesis; D009126:Muscle Relaxation / Q000187:drug effects; D009130:Muscle, Smooth / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D019001:Nitric Oxide Synthase; D011493:Protein Kinase C / Q000494:pharmacology*; D011817:Rabbits; D013270:Stomach / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology
chemical_list: D002956:Citrulline; D014660:Vasoactive Intestinal Peptide; D019001:Nitric Oxide Synthase; D000594:Amino Acid Oxidoreductases; D011493:Protein Kinase C; D002118:Calcium