title: Arginine vasopressin increases nitric oxide synthesis in cytokine-stimulated rat cardiac myocytes.
abstract: We investigated the effects of arginine vasopressin (AVP) on nitric oxide (NO) synthase activity in cardiac myocytes by measuring the production of nitrite, a stable metabolite of NO, and the expression of inducible NO synthase (iNOS) mRNA and protein. Incubation of cultured neonatal rat cardiac myocytes for 24 hours with interleukin-1beta (IL-1beta) caused a significant increase in NO production. Both AVP and V1a receptor agonist [Phe2,Ile3,Orn8]vasopressin augmented NO synthesis in IL-1beta-stimulated, but not in unstimulated myocytes, in a dose-dependent manner. The V1a receptor antagonist [d(CH2)[5]1,O-Me-Tyr2,Arg8]vasopressin completely inhibited the effect of AVP. The AVP-induced NO production by IL-1beta-stimulated cells was accompanied by increased iNOS mRNA and protein accumulation. AVP caused a significant increase in cytosolic free Ca2+ levels of cardiac myocytes, whereas it showed no effect on cytosolic cAMP levels. After protein kinase C activity was functionally depleted by treating cells with phorbol 12-myristate 13-acetate for 24 hours, AVP did not augment IL-1beta-induced NO production. The effect of AVP was also inhibited in the presence of the protein kinase C inhibitor calphostin C. The addition of AVP increased protein kinase C activity in cardiac myocytes, and its effect was significantly inhibited in the presence of calphostin C. These results support the hypothesis that the heart may be a target organ for AVP and that AVP modulates IL-1beta-induced iNOS expression in myocytes through the V1a receptor, which is mediated at least partially via activation of protein kinase C.
authors.affiliation: Department of Cardiology, Jichi Medical School, Minamikawachi, Tochigi, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Yamamoto
authors.forename: U
authors.initials: U
authors.lastname: Ikeda
authors.forename: K
authors.initials: K
authors.lastname: Okada
authors.forename: T
authors.initials: T
authors.lastname: Saito
authors.forename: Y
authors.initials: Y
authors.lastname: Kawahara
authors.forename: M
authors.initials: M
authors.lastname: Okuda
authors.forename: M
authors.initials: M
authors.lastname: Yokoyama
authors.forename: K
authors.initials: K
authors.lastname: Shimada
mesh_terms: D000818:Animals; D001127:Arginine Vasopressin / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism; D016207:Cytokines / Q000494:pharmacology*; D003600:Cytosol / Q000378:metabolism; D004790:Enzyme Induction; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D009569:Nitric Oxide / Q000096:biosynthesis*; D019001:Nitric Oxide Synthase / Q000235:genetics / Q000378:metabolism; D009573:Nitrites / Q000378:metabolism; D009994:Osmolar Concentration; D011493:Protein Kinase C / Q000502:physiology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D016207:Cytokines; D009573:Nitrites; D012333:RNA, Messenger; D001127:Arginine Vasopressin; D009569:Nitric Oxide; D000242:Cyclic AMP; D019001:Nitric Oxide Synthase; D011493:Protein Kinase C; D002118:Calcium