Role of angiotensin II in renal wrap hypertension

The role of angiotensin II in the development of renal wrap hypertension was studied in rabbits that underwent either bilateral renal cellophane wrap or sham operation. In half the rabbits, angiotensin II production was blocked by continuous administration of enalapril. Four weeks after renal wrapping, mean arterial pressure had risen by 48 +/- 5 mm Hg in untreated rabbits, but by only 25 +/- 4 mm Hg in enalapril-treated rabbits (p less than 0.01). Similar differences were also measured 6 weeks after wrapping. In untreated rabbits, plasma renin activity had increased fourfold 4 and 6 weeks after renal wrapping. There were no significant changes in blood pressure or plasma renin activity following sham operation. Compared with that in sham-operated rabbits, renal blood flow was reduced by 60% in the untreated rabbits 4 weeks after wrapping but by only 30% in the enalapril-treated wrapped rabbits (p less than 0.05). Renal vascular resistances were 5.5 +/- 1.7 mm Hg . ml-1 . min-1 and 1.2 +/- 0.1 mm Hg . min . ml-1 in the untreated wrapped and sham-operated rabbits respectively and 1.9 +/- 0.4 mm Hg . min . ml-1 and 0.8 +/- 1 mm Hg . min . ml-1 in the enalapril-treated wrapped and sham-operated rabbits. Renal wrapping did not alter filtration fraction in untreated rabbits, but markedly reduced it in enalapril-treated rabbits. These results suggest that angiotensin II had two major effects in rabbits after bilateral renal wrapping: it contributed substantially to the increase in blood pressure and caused renal vasoconstriction, primarily at a postglomerular site.