Urotensin-II is a nitric oxide-dependent vasodilator in the pial arteries of the newborn pig.
Urotensin-II (UT-II) is a small circular peptide and is described as the most potent endogenous vasoconstrictor in various vascular beds. However, the in vivo effects of UT-II can be either vasoconstriction or vasodilation depending on the species and the tissue investigated. The present study sought to characterize the vasoactive effect of UT-II in the piglet cerebral circulation in vivo. Pial arteries of 99 +/- 6 microm were visualized with intravital microscopy through a closed cranial window in anesthetized newborn piglets. Topical application of UT-II elicited a weak dose-dependent vasodilation of the arteries (0.001 microM: 3 +/- 3 microm, 0.1 microM: 10 +/- 5 microm, 10 microM: 14 +/- 7 microm). Smaller arteries with an initial diameter below 100 microm showed minimal or no vasodilation, while larger arteries between 100 and 120 microm had a pronounced dose-dependent effect. Systemic application of 15 mg/kg Nomega-nitro-L-arginine-methyl ester (L-NAME) completely inhibited the vasodilation. We conclude that UT-II, in contrast to most other vascular beds, is a weak NO-dependent vasodilator in the piglet pial vasculature.
Lacza
Zsombor
Z
Department of Physiology/Pharmacology, Wake Forest University Health Sciences, Medical Center Blvd., Winston-Salem, NC 27157, USA. zlacza@mac.com
W Busija
David
D
D000287:Administration, Topical; D000818:Animals; D000831:Animals, Newborn; D002536:Cerebral Arteries / Q000187:drug effects* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004336:Drug Antagonism; D005260:Female; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism*; D013552:Swine / Q000502:physiology; D014579:Urotensins / Q000494:pharmacology*; D014665:Vasodilator Agents / Q000494:pharmacology*
D014579:Urotensins; D014665:Vasodilator Agents; D009569:Nitric Oxide; C029677:urotensin II; D019331:NG-Nitroarginine Methyl Ester