The capillarity of left ventricular tissue of rats subjected to coronary artery occlusion.

Abstract

The effects of chronic coronary occlusion on the capillarity of left ventricular tissue in rat heart. The heart was exposed through a left-sided thoracotomy in ethylether-anesthetized and ventilated rats. The left coronary artery was occluded with a thin suture and the thorax was closed. Thirty days after the surgery the heart was removed and cross-sections were made for morphometric analyses. The cross-sectional area of cardiomyocytes increased markedly in the subepi- and subendocardia with a concomitant increase in the capillary to myocyte ratio. The total capillary density increased in the non-ischemic zone. The balance between the increase in capillary density and myocyte hypertrophy was assessed from the capillary domain area (CDA). CDAs were significantly smaller for the venular capillary portion in the subendocardial non-ischemic zone. However, CDAs in the transition zone around the necrosis were significantly increased in the venular capillary portion in the subendocardium and in all capillary portions in the subepicardium compared with those in the non-ischemic zone. Immunohistological staining for basic fibroblast growth factor (bFGF) revealed punctate bFGF distribution in both the non-ischemic and transition zones of ventricular tissues 30 days after occlusion, suggesting a persistent stimulation for capillary angiogenesis. The remodelling of the capillary bed is not uniform throughout the cardiac tissue in coronary-occluded rat hearts. CDAs decreased in the non-ischemic zone but increased in the transition zone. The rate of capillary angiogenesis failed to parallel the development of hypertrophy in the transition zone over 30 days, as could be seen from the significant reduction in the percentage of venular capillary portions.