GEOMETRY OF CAPILLARY NETWORKS IN VOLUME OVERLOADED RAT-HEART

Volume overload cardiac hypertrophy was induced in male Sprague-Dawley rats by experimental aortocaval fistula. This procedure resulted in considerable increases in left ventricular mass (70%) by 21-23 days. Our objective was to study the effect of volume overload on the geometry of coronary capillaries in the left ventricular midmyocardium. Tissue sections were stained according to a protocol that distinguished arteriolar (AC) and venular (VC) capillary regions by color. Morphometric data were then collected and compared between AC and VC regions. In sham-operated controls (CON; n = 8), the tissue area (capillary domain) supplied by a single capillary decreased from AC to VC regions (AC = 505 ± 5 μm2; VC = 452 ± 7 μm2; P < 0.01; mean ± SE). In volume overloaded hearts (VOL; n = 8), only VC domain areas were reduced from control values (P < 0.01) and the differences between AC and VC regions were preserved (AC = 480 ± 5 μm2; VC = 395 ± 6 μm2; P < 0.01). Minimal capillary length was significantly longer in volume overloaded hearts (VOL = 723 ± 18; CON = 581 ± 20 μm; P < 0.01). In the control group, AC segment length was longer than VC segment length (AC = 93 ± 2 μm; VC = 74 ± 2 μm; P < 0.01). In volume overload, AC segment length was also longer than VC segment length, but the divergence between AC and VC regions was increased (AC = 108 ± 3 μm; VC = 71 ± 2 μm; P < 0.01). These changes in capillary geometry may be secondary to specific changes in the arrangement and dimension of myocytes in the left ventricular wall following volume overload hypertrophy. © 1991.