[Protective effect and mechanism of morphine on acute myocardial ischemia/reperfusion injury in rats].
OBJECTIVE
To explore the protective effect of morphine and its mechanism on acute myocardial ischemia/reperfusion (AMIR) injury in rats, by the method of detecting calcitonin gene-related peptide (CGRP) and endothelin-1 (ET-1) levels, as well as myocardial infarct size.


METHODS
Forty SD rats were randomly divided into four groups: ischemia/reperfusion group (n=10), morphine preconditioning group (n=10), morphine and naloxone hydrochloride group (n=10), and normal controls (n=10). The animal model of AMIR was established in rats. The left anterior descending branch (LAD) of rat coronary was tied and un-tied. Animals were then sacrificed and hearts were harvested to determine myocardial infarct size by 2, 3, 5-triphenyl tetrazolium chloride (TTC). Radioimmunoassay was used to detect CGRP and ET-1 levels in plasma, and routine method was used to measure creatine kinase isoenzyme (CK-MB) in serum.


RESULTS
Plasma ET-1 and CGRP levels were increased significantly than that in normal controls in acute myocardial infarction (AMI) at 10 minutes of LAD tied (all P<0.01). Plasma ET-1 and CK-MB levels in morphine preconditioning group in AMIR at 45 hours of reperfusion were decreased significantly as compared with that in the same group in AMI at 10 minutes, and myocardial infarct size decreased significantly (all P<0.01), while, plasma CGRP levels were markedly increased. Significant differences in those parameters were found between morphine preconditioning group and morphine combined with naloxone hydrochloride group (all P<0.01).


CONCLUSIONS
Intravenous morphine has protective effects on AMI by increased plasma CGRP level, decreased plasma ET-1 level, and reduced myocardial infarct size.
Zhang
Zheng-yi
ZY
Department of Lanzhou Emergency Center, The Second Affiliated Hospital of Lanzhou Medical College, Lanzhou 730030, Gansu, China.
Li
Pei-jie
PJ
Chen
Tian-duo
TD
Yang
Lan
L
Zhao
Jian-hong
JH
Na
Tao
T
Tang
Xiao-qing
XQ
D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000097:blood; D004195:Disease Models, Animal; D019332:Endothelin-1 / Q000097:blood; D005260:Female; D019157:Ischemic Preconditioning, Myocardial; D008297:Male; D009020:Morphine / Q000627:therapeutic use*; D009203:Myocardial Infarction / Q000097:blood / Q000150:complications / Q000473:pathology; D015428:Myocardial Reperfusion Injury / Q000209:etiology / Q000517:prevention & control*; D009206:Myocardium / Q000473:pathology; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley
D019332:Endothelin-1; D009020:Morphine; D015740:Calcitonin Gene-Related Peptide