Coronary microvasculature alteration in hypertensive rats. Effect of treatment with a diuretic and an ACE inhibitor

The development of hypertension is accompanied by rarefaction of arterioles and capillaries in both animal models and humans. Although many studies have examined the effects of antihypertensive therapies on hemodynamics, cardiac hypertrophy, and large vessel structure, the question of whether changes in microvascular density induced by hypertension can be restored by pharmacologic treatment has yet to be answered. We report a series of experiments performed in rats with renovascular hypertension induced by unilateral nephrectomy and renal artery stenosis (Goldblatt one-kidney, one-clip model). Animals were treated for 4 weeks, after renal artery clipping, either with an angiotensin converting enzyme inhibitor (perindopril [PER], 0.76 mg/kg/day), or with an indol derivative diuretic with specific vascular properties (indapamide [IDP], 0.24 mg/kg/day) or with the combination of both drugs at the same doses as during monotherapy. Coronary microvessel densities (arterioles and capillaries) were evaluated by double immunolabeling in nonserial cryostat sections of the left ventricular inner myocardium. After 4 weeks of hypertension (mean arterial pressure, 174 ± 11 v 124 ± 5 mm Hg in normotensive (NT) controls, P< .01), cardiac hypertrophy (+59%, P< .001) was associated with a significant increase in myocardial arteriolar density (+27%, P< .01), and a decrease in capillary density (−12%, P< .05). Treatment with PER prevented the increase in arterial pressure, heart weight, and arteriolar density, but did not significantly affect the low coronary capillary density in comparison with that measured in untreated hypertensive (HT) rats. Treatment with IDP preserved normal capillary myocardial density but did not significantly lower the blood pressure (BP) (169 ± 9 mm Hg) and only slightly reduced the cardiac ventricular hypertrophy: −14% v untreated HT (P< .05) and +37% v NT (P< .01). In the same way, IDP normalized the left ventricular capillary density in spontaneously HT rats (+18% v untreated rats, P< .01). The combination of both drugs, PER and IDP, at the same low doses as during monotherapy, resulted in normal levels of arterial pressure and complete normalization of cardiac hypertrophy and arteriolar and capillary myocardial densities. In conclusion, the results observed after PER suggest that blockade of the renin-angiotensin system could inhibit large coronary vessel growth but minimally affects the capillary density despite complete normalization of BP. Indapamide could have beneficial effect on myocardial capillary density. The combination of IDP and PER has additional effects and prevents the increase in BP and cardiac weight, and reverses microvascular rarefaction, specifically arteriolar and capillary densities.