THE CAPILLARITY OF LEFT-VENTRICULAR TISSUE OF RATS SUBJECTED TO CORONARY-ARTERY OCCLUSION

Objective: The effects of chronic coronary occlusion on the capillarit y of left ventricular tissue in rat heart. Methods: The heart was expo sed through a left-sided thoracotomy in ethylether-anesthetized and ve ntilated rats. The left coronary artery was occluded with a thin sutur e and the thorax was closed. Thirty days after the surgery the heart w as removed and cross-sections were made for morphometric analyses. Res ults: The cross-sectional area of cardiomyocytes increased markedly in the subepi- and subendocardia with a concomitant increase in the capi llary to myocyte ratio. The total capillary density increased in the n on-ischemic zone. The balance between the increase in capillary densit y and myocyte hypertrophy was assessed from the capillary domain area (CDA). CDAs were significantly smaller for the venular capillary porti on in the subendocardial non-ischemic zone. However, CDAs in the trans ition zone around the necrosis were significantly increased in the ven ular capillary portion in the subendocardium and in all capillary port ions 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 tra nsition zones of ventricular tissues 30 days after occlusion, suggesti ng a persistent stimulation for capillary angiogenesis. Conclusion: Th e remodelling of the capillary bed is not uniform throughout the cardi ac tissue in coronary-occluded rat hearts. CDAs decreased in the non-i schemic zone but increased in the transition zone. The rate of capilla ry angiogenesis failed to parallel the development of hypertrophy in t he transition zone over 30 days, as could be seen from the significant reduction in the percentage of venular capillary portions.