Longitudinal study of the hindquarter vasculature during development in spontaneously hypertensive and Dahl...

The purpose of this study was to examine vascular structural alterations longitudinally in spontaneous and Dahl genetic hypertension. Hypertensive and control animals were studied at 5,9-11, and 17-19 weeks of age to permit analysis of prehypertensive, early and established hypertensive stages. Minimal and maximal resistance of the hindquarter vasculature was used as a functional assessment of structural alterations. At 5 weeks of age, the minimal vascular resistance of the spontaneously hypertensive rats (SHR) was elevated over Wistar-Kyoto (WKY) (p less than 0.02) but there was no difference between Dahl salt-sensitive (S) and resistant (R) rats. In both sets of animals, the minimal vascular resistance of the hypertensive group was significantly elevated over controls with age: p less than 0.001 in SHR; p less than 0.001 in Dahl S. The maximal vasoconstrictor response was significantly greater with age in SHR than in WKY, (p less than 0.001), but was not different in Dahl S compared to R. Thus, structural alterations, determined by assessing minimal vascular resistance, are present in both spontaneous and Dahl salt-sensitive hypertension, but the origin of the two differ. An increase in smooth muscle mass, assessed by maximal constriction, contributes importantly to the structural alterations in spontaneous hypertension; in Dahl S, other factors appear to contribute to structural alterations. Further, structural alterations precede frank hypertension in SHR but not in Dahl S hypertension.