Innate protection of baboon myocardium: effects of coronary artery occlusion and reperfusion. Shen, You-Tang, John T. Fallon, Mitsunori Iwase, and Stephen F. Vatner. Departments of Medicine, Harvard Medical School, Brigham & Women's Hospital, Boston, MA 02115 and the New England Regional Primate Research Center, Southborough, MA 01772
APStracts 2:0490H, 1995.
To determine whether the extent of myocardial infarction differs in conscious baboons and pigs, both devoid of preformed collaterals, the effects of 40 min and 90 min coronary artery (CA) occlusion (O) both followed by 4-7 days of CA reperfusion (R) were examined in both species. CAO reduced both subendocardial and subepicardial blood flows similarly, almost to zero, in both baboons and pigs for the entire CAO period. At 24 hr CAR, subendocardial blood flow had almost returned to pre-CAO control levels in baboons, but remained significantly depressed in pigs. The major difference in hemodynamics during CAO and CAR was observed for left ventricular end-diastolic pressure, which rose by 6+/-1 mmHg in pigs over the initial 24 hr reperfusion period, but did not change significantly in baboons. These data on recovery of subendocardial blood flow and left ventricular end-diastolic pressure suggest that larger infarcts would be observed in pigs than baboons. Indeed, infarct size/area at risk (IF/AAR) was significantly greater (p&LT0.05) in pigs (53+/-4.9%) than in baboons (17+/-2.9%) with 90 min CAO and 4-7 days CAR. With 40 min CAO and 4-7 days CAR, IF/AAR was 46+/-3.6% in pigs, while in baboons the IF/AAR was minimal, i.e., 2+/-0.6%. Thus, both pigs and baboons were characterized by minimal coronary collateral circulation, but infarct size in conscious baboons was significantly less, as compared with conscious pigs. Potentially, these differences could be explained, in part, by natural protective mechanisms and/or less reperfusion injury in primates. These results in primates may also help to explain the salutary effects of CAR in patients at intervals longer than have been demonstrated beneficial in other experimental animals. 

Received 14 July 1995; accepted in final form 25 October 1995.
APS Manuscript Number H654-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 November 95