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  • Title: Hemodynamics and microcirculatory alterations in reduced renal mass hypertension.
    Author: Lombard JH, Hinojosa-Laborde C, Cowley AW.
    Journal: Hypertension; 1989 Feb; 13(2):128-38. PubMed ID: 2914735.
    Abstract:
    The objectives of this study were to determine the hemodynamic and microcirculatory changes that occur during reduced renal mass hypertension in rats. In conscious animals with 75% reduction of total renal mass, mean arterial pressure was initially (4-8 hours) elevated by 15-20 mm Hg during intravenous infusion with isonatremic (145.4 mM) NaCl. Cardiac index was elevated by 15-20%, and total peripheral resistance index was normal or reduced. Cardiac index subsequently returned toward normal, but mean arterial pressure remained elevated (20-40 mm Hg), presumably because of an elevated total peripheral resistance. Cremasteric arterioles were actively constricted (35-50%) in rats with short-term (36 hours), but not chronic (5-6 weeks) reduced renal mass hypertension. Total microvessel density was approximately 15% lower in maximally dilated cremaster muscles of chronically hypertensive rats versus sham-operated controls, which suggests that arterioles are lost during sustained reduced renal mass hypertension. Arteriolar constriction in response to increased superfusate PO2 (0% to 5% O2) was 2-4 times greater in rats with both short-term and chronic reduced renal mass hypertension than in normotensive controls, which suggests that oxygen-dependent autoregulatory mechanisms are altered. The hemodynamic and microcirculatory alterations observed in these experiments suggest that classic short-term autoregulatory mechanisms and an enhanced response of arterioles to increased oxygen availability contribute to the elevated total peripheral resistance in short-term reduced renal mass hypertension, whereas structural changes and altered vascular oxygen responses contribute to an elevated microvascular resistance in chronic reduced renal mass hypertension.
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