[Distribution, content and action site of leucine-enkephalin in pulmonary artery wall of rat and rabbit].
Using immunohistochemical method to investigate the distribution of peptidergic fibers in the pulmonary artery wall of SD rat, L-enkephalin immunoreactive (L-ENK ir) fibers were easily demonstrated. The contents of L-ENK in pulmonary artery of rat and rabbit measured by radioimmunoassay were respectively 439.18 +/- 30.52 and 29.9 +/- 1.4 (pg/mg of wct tissue). Contraction of superfused strips of pulmonary artery of rabbit could be evoked by parameter I electric field stimulation. The response was blocked by alpha-receptor antagonist phentolamine. Alpha 2-receptor antagonist Yohimbine enhanced the response in small doses (0.06-0.12 mumol/L), while inhibited in large (3.2 mumol/L). The contraction could also be enhanced when the artery strips were preincubated with naloxone. After the alpha-receptors were blocked with phentolamine, stronger contraction could still be evoked by parameter II electric field stimulation and the response was not affected by naloxone. L-ENK had no effect on the contraction evoked by exogenous NE. The present experiments demonstrate that enkephalin presented in the pulmonary artery wall are released by electric field stimulation. Enkephalin may reduce the release of NE from sympathetic nerve endings via opioid receptors and inhibit the contraction response.
Yuan
X P
XP
Department of Pathophysiology, Fourth Military Medical University, Xi'an.
Lin
S X
SX
Yuan
S L
SL
Qin
B Z
BZ
Ma
D
D
D000818:Animals; D004558:Electric Stimulation; D004743:Enkephalin, Leucine / Q000378:metabolism*; D005260:Female; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects; D009638:Norepinephrine / Q000494:pharmacology; D011651:Pulmonary Artery / Q000737:chemistry*; D011817:Rabbits; D011863:Radioimmunoassay; D051381:Rats; D017207:Rats, Sprague-Dawley
D004743:Enkephalin, Leucine; D009638:Norepinephrine