Functional and structural changes in veins in spontaneous hypertension.

Six month old spontaneously hypertensive rats (SHR) and age and sex matched normotensive Wistar-Kyoto rats (WKY) were examined to evaluate the existence of functional and structural changes in the portal vein (PV), inferior vena cavae (IVC) and pulmonary arteries (PA). PV, central nervous and systolic right ventricular pressures did not differ in the anesthetized SHR when compared with WKY, despite elevated systolic arterial pressure. PV, IVC and PA obtained from SHR were less extensible, developed more tension, exhibited an enhanced sensitivity to serotonin and a thromboxane-like prostanoid, accumulated more of the protein precursors 2-14C-leucine, 2-14C-glucosamine, 7-3H-fucose, exhibited a normal rate of uptake of 2-14C-thymidine, and increased protein content and a decreased concentration of DNA. When examined under light and electron microscopy, the veins and PA obtained from SHR demonstrated medial smooth muscle hypertrophy, and increased density of PAS-Schiff positive stain, enlarged and prominent Golgi apparati and an increased cell diameter through the region of the nucleus. These changes were not due to water-logging since the water content of the veins and PA from SHR and WKY did not differ. These data support the conclusion that PV, IC and PA obtained from SHR exhibit functional and structural changes independent of increases in intravenous pressure. These changes may relate to the increase in blood vessel protein.