Effect of arginine vasopressin on the canine epicardial coronary artery: experiments on V1-receptor-mediated production of nitric oxide.
OBJECTIVE
To determine whether arginine vasopressin releases endothelium-derived nitric oxide (EDNO) from the epicardial coronary artery.


METHODS
We studied segments of canine left circumflex coronary arteries suspended in organ chambers to measure isometric force. The coronary artery segments were contracted with prostaglandin F2alpha (2 x 10-6M) and exposed to a unique, strong arginine vasopressin concentration (10-6M) or titrated concentrations (10-9 a 10-5 M).


RESULTS
The unique dose of arginine vasopressin concentration (10-6M) induced transient, but significant (p<0.05), relaxation in arterial segments with endothelium, and an increase, not significant, in tension in arteries without endothelium. Endothelium-dependent relaxation to arginine vasopressin was inhibited by Ng-monomethyl-L-arginine (L-NMMA, 10-5M) or N G-nitro-L-arginine (L-NOARG) (10-4M), 2 inhibitors of nitric oxide synthesis from L-arginine. Exogenous L-arginine (10-4M), but not D-arginine (10-4M), reversed the inhibitory effect of L-NMMA on vasopressin-mediated vasorelaxation. Endothelium dependent relaxation to vasopressin was also reversibly inhibited by the vasopressin V1-receptor blocker d(CH2)5Try(Me) arginine vasopressin (10-6M) (n=6, P<0.05).


CONCLUSIONS
Vasopressin acts through V1 endothelial receptors to stimulate nitric oxide release from L-arginine.
Evora
Paulo Roberto B
PR
Mayo Clinic, Mayo Foundation, Rochester, MN, USA. prbevora@keynet.com.br
Pearson
Paul J
PJ
Rodrigues
Alfredo J
AJ
Viaro
Fernanda
F
Schaff
Hartzell V
HV
D000818:Animals; D001120:Arginine / Q000494:pharmacology; D001127:Arginine Vasopressin / Q000494:pharmacology*; D003331:Coronary Vessels / Q000187:drug effects* / Q000378:metabolism; D004285:Dogs; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000378:metabolism; D045462:Endothelium-Dependent Relaxing Factors / Q000037:antagonists & inhibitors; D005260:Female; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism*; D010496:Pericardium / Q000187:drug effects* / Q000378:metabolism; D017483:Receptors, Vasopressin / Q000378:metabolism*; D014662:Vasoconstrictor Agents / Q000494:pharmacology*; D014664:Vasodilation / Q000502:physiology
D045462:Endothelium-Dependent Relaxing Factors; D017483:Receptors, Vasopressin; D014662:Vasoconstrictor Agents; D001127:Arginine Vasopressin; D009569:Nitric Oxide; D001120:Arginine