Endomorphins inhibit contractile responses of rat thoracic aorta rings induced by phenylephrine and angiotensin II in vitro.
Abstract
AIM: 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).
CONCLUSION: 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.
Keywords:
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).
CONCLUSION: 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.