Total venous capacity in two-kidney, one clip Goldblatt hypertensive rats

To assess possible time-related changes in total venous capacity, mean circulatory filling pressure (MCFP) and blood volume (BV, Evans blue) were determined in conscious rats with early, intermediate and chronic phases of two-kidney, one clip Goldblatt hypertension. MCFP, and index of whole-body venous activity, was measured while the circulation was arrested by the brief inflation of a balloon inserted into the right atrium. Compared with shamoperated control rats, Goldblatt rats showed unchanged MCFP and BV in early phase, unchanged MCFP with marginally (0.05 less than p less than 0.10) decreased BV in intermediate phase, and significantly (p less than 0.05) increased MCFP with unchanged BV in chronic phase. Thus, decreased total venous capacity, which is reflected in increased MCFP relative to BV, occurred with a continuation of hypertension. MCFP/BV curves, obtained by measuring MCFP before and after rapid BV change, appeared to shift toward the pressure axis in all Goldblatt groups. There were no significant differences in total vascular compliance, which is the inverse of the slope of this curve and is an index of total venous compliance, between Goldblatt and control groups at any time-period studied. These results suggest that decreased venous capacity observed in chronic hypertensive rats may be a secondary hemodynamic state and may not be related to decreased venous compliance.