Loss of myocardial protection of ischemic preconditioning
correlates with the decay of increased ecto-5'-nucleotidase
activity.
Minamino;, Tetsuo, Masafumi Kitakaze; Toshikazu Morioka; Koichi Node;
Kazuo Komamura; Hiroshi Takeda; Michitoshi Inoue; Masatsugu Hori; and
Takenobu Kamada.
The First Department of Medicine, Osaka University School of
Medicine, Osaka and The Department of Information Science, Osaka
University Hospital, Osaka, Japan
APStracts 2:0333H, 1995.
We investigated whether loss of myocardial protection after ischemic
preconditioning (IP) is related to the extent of deactivation of
activated ecto-5'-nucleotidase. The coronary arteries of mongrel dogs
were occluded 4 times for 5 minutes separated by 5 minutes of
reperfusion (IP). Five (IP1), 30 (IP2), 60 (IP3) and 120 (IP4)
minutes after the 4th 5 minute-coronary occlusion or following
corresponding nonischemic period (control groups), the coronary
arteries were occluded for 90 minutes followed by 6 hours of
reperfusion. The infarct size-limiting effect of IP gradually
disappeared in the IP2 (21.6+3.9%) and IP3 (33.8+3.6%) groups
compared with the IP1 group (8.3+1.6%), and returned to the control
level in the IP4 group (39.9+5.2%). The increased ecto-5'
-nucleotidase activity due to the IP procedure decreased according to
the order of IP1 to IP4 groups. Infarct size was inversely correlated
with ecto-5'-nucleotidase activity (P<0.001). An inhibitor of
ecto-5'-nucleotidase blunted the infarct size-limiting effect of IP.
The infarct size-limiting effect of IP decreased as the activation of
ecto-5'-nucleotidase was blunted. These results suggest that ecto-5'
-nucleotidase activity plays a key role in the cardioprotection of IP.
Received 6 March 1995; accepted in final form 11 July 1995.
APS Manuscript Number H207-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 14 August 1995.