Altered venous function in hypertensive rats.

The vascular beds of the upper or lower body of rats were perfused through the aorta with oxygenated Krebs-Ringer solution containing dextran (7 g/100 ml), at 37 degrees C. Perfusion was stopped every 10 minutes, and the pressure rise in the jugular or the femoral vein was recorded during rapid infusion (15.3-90.0 ml/min) of Krebs-Ringer solution into the inferior vena cava. The following groups of rats were studied: (1) six male genetically hypertensive rats (GHR), 9-11 months old, New Zealand strain; (2) seven female GHR, 5-6 months old, New Zealand strain; (3) eight male spontaneously hypertensive rats (SHR), 4 months old, Okamoto strain; (4) five male rats with two-kidney Goldblatt hypertension (2-KGH), 30 days postclipping; (5) seven male 2-KGH rats, 65 days postclipping; (6) eight male rats with one-kidney Goldblatt hypertension (1-KGH), 40 days postclipping; (7) weight- and sex-matched normotensive control rats of the appropriate strain; and (8) weight- and sex-matched two-kidney and one-kidney, sham-clipped normotensive rats. Preliminary studies showed that rapid infusion into the venous circulation fills the veins, but there is no entry of fluid into the arterial side of the circulation. Compared to controls, the venous pressure-volume curves of GHR (male and female), SHR, 1-KGH rats and 2-KGH rats, 65 (but not 30) days postclipping, were shifted toward the pressure axis (P less than 0.05). The shift of the venous pressure-volume curves persisted following the reduction of vasoconstrictor tone by killing the rats or by the administration of sodium nitroprusside (0.1 mg/ml perfusate), or by both. The findings suggest decreased venous capacity in hypertensive rats.