Modulation of tubuloglomerular feedback by angiotensin II type 1 receptors during the development of Goldblatt hypertension.

It has been suggested that the increased levels of angiotensin II (Ang II) in the contralateral kidney of two-kidney, one clip (2K1C) Goldblatt hypertensive rats act to enhance tubuloglomerular feedback responsiveness and proximal tubular reabsorption and thereby exert a substantial sodium-retaining influence on the nonclipped kidney. The current study investigated the Ang II dependency of tubuloglomerular feedback responsiveness in the nonclipped kidney during the early stages of development of 2K1C hypertension. Stop-flow pressure feedback responses were assessed in the nonclipped kidney of 2K1C rats during control conditions and after systemic administration of the Ang II type 1 receptor antagonist losartan (10 mg/kg). In 1-week clipped and sham-operated rats, losartan administration decreased mean arterial pressure (from 143 +/- 6 to 123 +/- 2 mm Hg, P < .01, and from 129 +/- 2 to 106 +/- 5 mm Hg, P < .01, respectively) and attenuated the magnitude of the maximal feedback responses (from -12.9 +/- 1.2 to -3.0 +/- 0.3 mm Hg, P < .01, and from -13.2 +/- 1.5 to -3.6 +/- 1.1 mm Hg, P < .01, respectively). The decreases in mean arterial pressure were not significantly different in sham-operated and 1-week clipped rats. In 3-week clipped rats, mean arterial pressure was further elevated (163 +/- 6 mm Hg) compared with sham-operated rats (134 +/- 4 mm Hg, P < .01).(ABSTRACT TRUNCATED AT 250 WORDS)