Microvascular changes in the heart during chronic arterial hypertension.

Changes of myocardial microvascular permeability in chronic renovascular arterial 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 beta-lipoprotein (CL/CP) 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 CL/CP 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-independent reflection coefficient (sigma) for each group. Sigma is a surface area-independent indicator of microvascular permeability when determined for specific protein molecules at high transmicrovascular fluid fluxes.(ABSTRACT TRUNCATED AT 250 WORDS)