Microvascular morphometry and perfusion in renal hypertension-induced cardiac hypertrophy

Abstract

This study examined alterations in microvascular morphometry and perfusion occurring concomitantly with changes in coronary blood flow (CBF), flow reserves, and coronary vascular resistance (CVR) in myocardial hypertrophy. New Zealand White rabbits (n = 28) with one-kidney, one-clip hypertension (1K,1C) or uninephrectomy (control) were examined 4 wk after surgery in anesthetized open-chest preparations. Animals were divided into two experimental series. In the first series, flows were determined with radioactive microspheres during rest and adenosine-induced vasodilation. In a second series, fluorescein isothiocyanate dextran (FITC-dextran) was injected to visualize the perfused arteriolar and capillary beds. The total vasculature was marked with an alkaline phosphatase stain. Mean arterial pressure was elevated in 1K,1C animals (110 +/- 7 mmHg, means +/- SE) when compared with controls (77 + 4 mmHg), and the myocardial weight was greater. Resting CBF was higher in 1K,1C animals compared with controls (227 +/- 21 vs. 168 +/- 12 ml.min-1.100 g-1), and the flow reserve was reduced. Minimal CVR was higher in 1K,1C compared with controls (0.190 +/- 0.035 vs. 0.091 +/- 0.018 mmHg.ml-1.min.100 g). The number of capillaries per squared millimeter was not different from control (2,448 + 121 vs. 2,216 +/- 132/mm2) and the percent perfused was similar (56 +/- 2 vs. 61 +/- 3%). The arteriolar density in cardiac hypertrophy was lower (1.2 +/- 0.2 vs. 2.1 +/- 0.3/mm2), and the percent perfused was higher (86 +/- 5 vs. 63 + 6%) compared with controls. Thus, in myocardial hypertrophy, the anatomical density and volume fraction of arterioles appears to be reduced, and the percentage of arterioles perfused increased.(ABSTRACT TRUNCATED AT 250 WORDS)