title: Chronotropic effects of cytokines and the nitric oxide synthase inhibitor, L-NMMA, on cardiac myocytes.
abstract: We and others have proposed that cytokine-stimulated nitric oxide (NO) production is responsible for reversible myocardial depression in sepsis, trauma and ischemia. An effect of NO on cardiac sarcolemmal L-type calcium channels has also recently been proposed. The spontaneous beating rate of neonatal cardiac myocytes is regulated by the sarcolemmal L-type calcium channel. Accordingly, we sought to determine if cytokine-stimulated NO production could also regulate beating rates of neonatal cardiac myocytes. Treatment of neonatal rat cardiac myocytes with TNF, IL-1, IL-6, 10(-5)M NMA, or 10(-3)M NMA significantly enhanced spontaneous beating rates compared to untreated myocytes in serum-free media for 48 hours (p < or = .01; n = 12 for each). Only IL-1 treatment resulted in significant nitrite levels vs. control over 48 hours (4.2 +/- 0.7 vs. 0.3 +/- 0.2 nmoles/1.25 x 10(-5) cells, respectively) (n = 12). Nitrite production by IL-1 was inhibited by 10(-3)M NMA but not 10(-5)M NMA (0.3 +/- 0.2 vs. 4.1 +/- 0.6 nmoles; p < .01; n = 12). The addition of 10(-5)M NMA to TNF, IL-1, and IL-6 did not alter the effect of the cytokines on the spontaneous beating rates of the cardiac cells (p < or = .01; n = 12 for each). These results strongly suggest that cytokines and NMA affect cardiac myocyte spontaneous beating rates through mechanisms independent of NO.
authors.affiliation: Department of Pathology, University of Pittsburgh School of Medicine, PA 15213-2582.
authors.forename: C V
authors.initials: CV
authors.lastname: Oddis
authors.forename: R L
authors.initials: RL
authors.lastname: Simmons
authors.forename: B G
authors.initials: BG
authors.lastname: Hattler
authors.forename: M S
authors.initials: MS
authors.lastname: Finkel
mesh_terms: D000594:Amino Acid Oxidoreductases / Q000037:antagonists & inhibitors*; D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D001120:Arginine / Q000031:analogs & derivatives* / Q000494:pharmacology; D002478:Cells, Cultured; D016207:Cytokines / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D006321:Heart / Q000187:drug effects / Q000502:physiology; D006339:Heart Rate / Q000187:drug effects*; D007375:Interleukin-1 / Q000494:pharmacology; D015850:Interleukin-6 / Q000494:pharmacology; D007700:Kinetics; D009569:Nitric Oxide / Q000037:antagonists & inhibitors; D019001:Nitric Oxide Synthase; D051381:Rats; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D019323:omega-N-Methylarginine
chemical_list: D016207:Cytokines; D007375:Interleukin-1; D015850:Interleukin-6; D014409:Tumor Necrosis Factor-alpha; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D001120:Arginine; D019001:Nitric Oxide Synthase; D000594:Amino Acid Oxidoreductases