Pressor response to norepinephrine (NE) infusion was examined in rabbits with renal artery stenosis (1-kidney, 1 clip Goldblatt) with 3-days' duration and sham operated rabbit. The 3-day clipped rabbits showed exaggerated pressor response to NE, though they did not develop hypertension with normal value for plasma renin activity (PRA). Infusion of two angiotensin II antagonists, [1-Sar, 8-Ileu] angiotensin II and [1-Sar, 8-Ara] angiotensin II which were different in amino acid residue in position 8, abolished completely the hyperresponse to NE. These results provide strong evidence that angiotensin II plays an important role in the exaggerated pressor response to NE in the prehypertensive rabbits : however, as a correlation between the value for PRA and for the increased pressor responsiveness to NE were not observed, additional mechanism (s) may be involved in the hyperresponsiveness to NE.
