The role of
angiotensin in three forms of experimental
hypertension was assessed in rats. First, the acute blood pressure response to injected
angiotensin amide and
angiotensin acid was determined. Rats made hypertensive with
deoxycorticosterone and saline showed exaggerated responses; rats made hypertensive by clipping one renal artery showed depressed responses; and rats made hypertensive by clipping one renal artery and contralateral
nephrectomy showed normal responsivity to
angiotensin amide but depressed responsivity to
angiotensin acid. These findings suggested that different mechanisms may be involved in the three types of
hypertension studied. To assess the role of
angiotensin in these hypertensive rats the blood pressure response, the presence of
antibodies determined by radioimmune techniques, and the degree of refractoriness to injected
angiotensin after immunization with
angiotensin were studied. None of six rats made hypertensive by
deoxycorticosterone and saline, and none of five mock immunized rats with
renal hypertension of both types had a fall in blood pressure. By contrast, of the 20 rats with both types of
renal hypertension in which antibody determinations were made, 11 had developed a significant antibody titer, of which seven showed a significant reduction in blood pressure at the time of antibody determination, and three of the remaining four had a significant blood pressure reduction earlier in their course. None of the nine renal hypertensive rats without demonstrable
antibodies had a reduced blood pressure at the time of antibody determination, and only one had an earlier reduction in blood pressure. The renal hypertensive rats were all refractory to injected
angiotensin after immunization. These results suggest a primary role for
angiotensin in both forms of
renal hypertension.