Effects of inducible nitric oxide synthase inhibition on the rat tail vascular bed reactivity three days after myocardium infarction.
The acute phase of myocardial infarction promotes an inflammatory response that stimulates inducible nitric oxide synthase (iNOS). We investigated the iNOS role on the rat tail vascular bed reactivity 3 days after myocardial infarction. Vasodilator and vasoconstrictor responses were determined in isolated caudal vascular beds from Wistar rats 3 days after coronary artery ligation (CAL) and sham-operated animals (SHAM). Rats were treated with the iNOS inhibitor S-methylisothiourea sulfate (SMT), 5 mg Kg day, i.p. or placebo. Concentration of plasma nitrite/nitrate (NOx) and the expression of iNOS mRNA in tail arteries were evaluated. The CAL group showed increased maximal vasoconstrictor response to phenylephrine (SHAM= 241 +/- 8; CAL= 288 +/- 13 mm Hg, P < 0.05) and SMT treatment normalized this effect (CAL-SMT = 253 +/- 7 mm Hg, P < 0.05). The sensitivity to acetylcholine was reduced in the CAL group, but SMT treatment did not alter this response. The plasma NOx and iNOS mRNA expression in tail arteries were increased in CAL rats. SMT treatment reduced the plasma NOx in the CAL group and the arterial expression of iNOS mRNA in SHAM and CAL group. In conclusion, iNOS inhibition prevented the increased phenylephrine reactivity in rat caudal vascular beds 3 days after myocardial infarction.
Sartório
Carmem Luíza
CL
Department of Physiological Sciences, Federal University of Espírito Santo, Vitória, ES, Brazil.
Pinto
Valber Dias
VD
Cutini
Gustavo Julio de Salles
GJ
Vassallo
Dalton Valentim
DV
Stefanon
Ivanita
I
D000818:Animals; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D009203:Myocardial Infarction / Q000201:enzymology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors* / Q000096:biosynthesis; D052247:Nitric Oxide Synthase Type II; D051381:Rats; D017208:Rats, Wistar; D013623:Tail / Q000098:blood supply* / Q000187:drug effects / Q000201:enzymology*; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology
D004791:Enzyme Inhibitors; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat