title: Hemodynamics and microcirculatory alterations in reduced renal mass hypertension.
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.
authors.affiliation: Department of Physiology, Medical College of Wisconsin, Milwaukee, TE 53226.
authors.forename: J H
authors.initials: JH
authors.lastname: Lombard
authors.forename: C
authors.initials: C
authors.lastname: Hinojosa-Laborde
authors.forename: A W
authors.initials: AW
authors.lastname: Cowley
mesh_terms: D000818:Animals; D001794:Blood Pressure; D006439:Hemodynamics; D006706:Homeostasis; D006977:Hypertension, Renal / Q000503:physiopathology*; D008297:Male; D008833:Microcirculation / Q000503:physiopathology*; D051381:Rats; D011919:Rats, Inbred Strains; D014655:Vascular Resistance; D014661:Vasoconstriction