Endomorphins inhibit contractile responses of rat thoracic aorta rings induced by phenylephrine and angiotensin II in vitro.
OBJECTIVE
To study the effects of opioid receptor agonists endomorphin-1 and -2 on contractile responses of rat thoracic aorta rings to phenylephrine (PE) and angiotensin II (Ang II), and their possible mechanism in vitro.


METHODS
Isometric tension recording was progressed in thoracic aorta rings from Wistar rats.


RESULTS
Pretreatment of morphine, endomorphin-1 and -2 (0.1, 1, and 10 micromol/L) could inhibit the contractile responses of the endothelium-intact aorta rings to PE (0.1 micromol/L) and Ang II ( 1 micromol/L) in a concentration-dependent manner (P < 0.01), but could not inhibit the contraction of rings without endothelium (P > 0.05). Naloxone (1 micromol/L) could partially antagonize the effects of endomorphine-1 and -2 (P < 0.01). N(omega)-nitro-L-arginine (L-NNA, 10 micromol/L) or endothelial rubbing could completely blocked the effects of morphine, endomorphine-1 and -2 (P < 0.01).


CONCLUSIONS
Endomorphin-1 and -2 could inhibit PE- and Ang II-induced contractions of rat aorta rings, which was partially by naloxone-sensitive mechanism and related to the release of nitric oxide from vascular endothelium.
Qi
Yuan-Ming
YM
Department of Biochemistry and Molecular Biology, School of Life Science, Lanzhou University, Lanzhou 730000, China.
Yang
Ding-Jian
DJ
Duan
Xin
X
Yang
Fan
F
Li
Shi-Rong
SR
Shen
Jian-Min
JM
Wang
Rui
R
D000701:Analgesics, Opioid / Q000494:pharmacology; D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D001013:Aorta, Thoracic / Q000502:physiology; D004347:Drug Interactions; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology*; D009842:Oligopeptides / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D010656:Phenylephrine / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D017450:Receptors, Opioid, mu / Q000819:agonists; D014662:Vasoconstrictor Agents / Q000494:pharmacology
D000701:Analgesics, Opioid; D009842:Oligopeptides; D017450:Receptors, Opioid, mu; D014662:Vasoconstrictor Agents; C105293:endomorphin 1; D000804:Angiotensin II; D010656:Phenylephrine; C105294:endomorphin 2