Microvascular changes in the heart during chronic arterial hypertension

Abstract

Changes of myocardial microvascular permeability in chronic renovascular hypertension were studied. Hypertension was induced in dogs utilizing a one-kidney, one-clip Goldblatt model. Systemic arterial pressure, coronary sinus pressure, systemic venous pressure, myocardial lymph flow rate, myocardial interstitial fluid pressure, and the lymph-to-plasma protein concentration ratio for total plasma proteins and for β-lipoprotein (C(L)/C(P)) were determined in control animals and 4-6 weeks following the Goldblatt procedure in hypertensive animals. Control values for the normotensive animals were 123 ± 17 mm Hg, 7.3 ± 1.3 mm Hg, 2.5 ± 2.1 mm Hg, 3.1 ± 2.1 ml/hr, 14.9 ± 3.1 mm Hg, 0.82, and 0.33, respectively, while control values for the chronically hypertensive dogs were 160 ± 20 mm Hg, 7.8 ± 1.9 mm Hg, 2.9 ± 2.5 mm Hg, 10.5 ± 2.5 ml/hr, 24.8 ± 3.7 mm Hg, 0.87, and 0.31, respectively. Under control conditions, myocardial lymph flow rate was significantly higher in the hypertensive group while no difference could be demonstrated in C(L)/C(P) between the two groups. This is indicative of either a change in myocardial microvascular permeability or an increase in microvascular exchange surface area. Coronary sinus pressure was elevated in both groups in order to increase transmicrovascular fluid flux and determine the filtration-dependent reflection coefficient (σ) for each group. σ is a surface area-independent indicator of microvascular peremability when determined for specific protein molecules at high transmicrovascular fluid fluxes. Although filtration independence for total plasma protein could not be reached in either group, σ for β-lipoprotein decreased from 0.96 in the normotensive group to 0.80 in the hypertensive group, indicating an increase in microvascular permeability. Our results indicate a significant increase in myocardial microvascular permeability to macromolecules resulting from the one-kidney, one-clip Goldblatt model of chronic arterial hypertension.