Endothelium-dependent relaxation in response to poly-L-arginine in canine coronary arteries: implications about hyperpolarization as a mechanism of vasodilatation.
OBJECTIVE
To study the mechanism by which poly-L-arginine mediates endothelium-dependent relaxation.


METHODS
Vascular segments with and without endothelium were suspended in organ chambers filled with control solution maintained at 37 C and bubbled with 95% O2 / 5% CO2. Used drugs: indomethacin, acetycholine, EGTA, glybenclamide, ouabain, poly-L-arginine, methylene blue, N G-nitro-L-arginine, and verapamil and N G-monomethyl-L-arginine. Prostaglandin F2  and potassium chloride were used to contract the vascular rings.


RESULTS
Poly-L-arginine (10-11 to 10-7 M) induced concentration-dependent relaxation in coronary artery segments with endothelium. The relaxation to poly-L-arginine was attenuated by ouabain, but was unaffected by glybenclamide. L-NOARG and oxyhemoglobin caused attenuation, but did not abolish this relaxation. Also, the relaxations was unaffected by methylene blue, verapamil, or the presence of a calcium-free bathing medium. The endothelium-dependent to poly-L-arginine relaxation was abolished only in vessels contracted with potassium chloride (40 mM) in the presence of L-NOARG and indomethacin.


CONCLUSIONS
These experiments indicate that poly-L-arginine induces relaxation independent of nitric oxide.
Evora
Paulo R B
PR
Laboratório de Função Endotelial, Divisão de Cirurgia Experimental, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil. prbevora@keynet.com.br
Pearson
Paul J
PJ
Rodrigues
Alfredo José
AJ
Viaro
Fernanda
F
Schaff
Hartzell V
HV
D000818:Animals; D003331:Coronary Vessels / Q000187:drug effects*; D004285:Dogs; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000502:physiology; D005260:Female; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects*; D009569:Nitric Oxide / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D010455:Peptides / Q000493:pharmacokinetics / Q000494:pharmacology*; D014664:Vasodilation / Q000187:drug effects; D014665:Vasodilator Agents / Q000494:pharmacology
D010455:Peptides; D014665:Vasodilator Agents; C015462:polyarginine; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase