EFFECT OF ACUTE CORONARY-OCCLUSION ON THE SIZE OF THE DYNAMICALLY PERFUSED CORONARY CAPILLARY BED IN THE DOG

The aim of the present study was to investigate the influence of reduc ed left anterior descending (LAD) coronary arterial blood flow on the size of the perfused coronary capillary surface area (CCSA) in dogs. T he transcoronary hydrolysis (nu) of the specific ACE substrate, [H-3]b enzoyl-Phe-Ala-Pro, was estimated and the parameter A(max)/K-m (propor tional to the size of the perfused CCSA) was calculated. By means of a ligature placed around the LAD, LAD blood flow was transiently reduce d to 36.0 +/- 4.1 (E-1) and 17.4 +/- 4.3% (E-2) of control; in a separ ate maneuver the first diagonal branch of the LAD was ligated to achie ve 40.0 +/- 6.7% (E-3) of control now. The nu values remained unchange d at around 0.7 for E-1, E-2, and E-3 determinations, suggesting unalt ered substrate transit time through the coronary capillary bed. A(max) /K-m values decreased to 36 +/- 5, 17 +/- 4, and 47 +/- 10% of control for E-1, E-2, and E-3 determinations, respectively, reflecting a flow -proportional decrease in CCSA. Values of the transpulmonary measures of nu and A(max)/K-m performed at the beginning and end of the protoco l were unchanged. These results support the hypothesis that reduction in coronary blood flow will produce proportional decreases in the size of the CCSA. This new procedure can thus serve as a useful tool for i nvestigating alterations in the size of the CCSA in different species and under various pathophysiologic challenges. (C) 1998 Academic Press .