Comparison of renin-specific IgG and antibody fragments in studies of blood pressure regulation

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Abstract
The use of antirenin antibody and its fragments as specific tools for the analysis of the role of renin in blood pressure regulation is assessed. Specific IgG or its antibody fragments (Fab) raised against purified canine renal renin were employed. These agents had no effect on blood pressure in the Na-replete unanesthetized dog but induced systemic vasodepressor response (16.4 .+-. 2 mm Hg mean pressure) and suppression of plasma renin activity in Na-deplete animals. Renin-specific IgG or Fab restored mean systemic pressure of acute renovascular hypertensive dogs to normotensive levels (132 .+-. 2 to 90 .+-. 5 mm Hg) associated with inhibition of plasma renin activity (11.2 .+-. 2-1.4 .+-. 0.7 ng angiotensin I .cntdot. ml-1 .cntdot. h-1). A linear relationship was demonstrated between the reduction in mean systemic pressure and fall in plasma renin activity (r = 0.87, P < 0.005). The onset of action of both agents occurred within minutes. The peak effect of Fab was observed within 1-2 min, while that of IgG was delayed by .apprx. 20 min. The duration of action of Fab was short lived [.apprx. 30 min) whereas that for IgG was prolonged (up to 24 h). The results demonstrate the usefulness of renin-specific IgG and Fab as tools in physiological studies.