MICROVASCULATURE IN ANGIOTENSIN II-DEPENDENT CARDIAC-HYPERTROPHY IN THE RAT

The long-lasting effect of angiotensin II (Ang II) on the microvascula ture in the rat left ventricle was studied. Immunolabeling of ventricu lar cryosections combined with morphometric analysis allowed us to (1) distinguish between capillaries and arterioles and (2) precisely eval uate their respective densities in the endomyocardium. Ang II-induced hypertensive cardiac hypertrophy was associated with an 18% decrease i n capillary density (P<0.05) and an increase in arteriole density (+54 %, P<0.001); Treatments with losartan or PD123319, the respective anta gonists of the angiotensin subtype 1 and subtype 2 receptors, prevente d the increase in arteriolar density, whereas only losartan, which res tored normal arterial pressure, prevented changes in capillary density . Taken together, these results indicate that Ang II-induced cardiac h ypertrophy was associated with capillary rarefaction and arteriolar gr owth, the 2 processes being independently regulated.