Relaxant effects of calcitonin gene-related peptide on isolated small renal arteries in stroke-prone spontaneously hypertensive rats.
The relaxant effects of calcitonin gene-related peptide (CGRP) on the 3rd branches of renal arteries obtained from stroke-prone spontaneously hypertensive rats (SHRSP), and Wistar-Kyoto rats (WKY) were investigated in vitro. CGRP elicited concentration-dependent relaxation, and the relaxant response was not affected by the mechanical removal of endothelium in either SHRSP or WKY. The CGRP-induced relaxant response was markedly greater in SHRSP than in WKY, whereas there was no significant difference in acetylcholine-induced relaxation, which was endothelium-dependent, between the two groups. Additionally, significantly enhanced reactivity to CGRP was also shown in spontaneously hypertensive rats compared to WKY; however, this reactivity was less than that observed in SHRSP. There were also no significant differences between WKY and SHRSP in the relaxation induced by forskolin, dibutyryl cyclic AMP, and 3-isobutyl-1-methylxanthine (IBMX). CGRP-induced relaxation was significantly potentiated in similar manner by the pretreatment with IBMX in both WKY and SHRSP. Incubation with glibenclamide (10(-6) M) had no effect on CGRP-induced relaxation in either group, the WKY or the SHRSP. These results suggest that CGRP produces endothelium-independent relaxation in the small renal arteries in the rat, and that the increased CGRP-induced relaxant response found in SHRSP may not be associated with the altered vasodilation mediated by cyclic AMP, or with functional changes in ATP-sensitive potassium channels.
Gao
Y
Y
Department of Pharmacology, Kinki University School of Medicine, Osaka, Japan.
Nishimura
Y
Y
Suzuki
A
A
Yoshida
K
K
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000494:pharmacology*; D005576:Colforsin / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005905:Glyburide / Q000494:pharmacology; D006973:Hypertension / Q000503:physiopathology; D066298:In Vitro Techniques; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D012077:Renal Artery / Q000187:drug effects*
D005576:Colforsin; D015740:Calcitonin Gene-Related Peptide; D000109:Acetylcholine; D005905:Glyburide