The effects of angiotensin-(1-7) on the exchanger NHE3 and on [Ca2+]i in the proximal tubules of spontaneously hypertensive rats

The acute effects of angiotensin-1–7 [ANG-(1–7)] on the reabsorptive bicarbonate flow (JHCO3–) were evaluated using stationary microperfusion in vivo in the proximal tubules of spontaneously hypertensive rats (SHR) and their normotensive controls, Wistar-Kyoto (WKY) rats, using a microelectrode sensitive to H+. In WKY rats, the control JHCO3– was 2.40 ± 0.10 nmol·cm–2·s–1 (n = 120); losartan (10–7 M) or A779 (10–6 M, a specific Mas antagonist), alone or in combination with losartan, decreased the JHCO3–. ANG-(1–7) had biphasic effects on JHCO3–: at 10–9 M, it inhibited, and at 10–6, it stimulated the flow. S3226 [10–6 M, a specific Na+-H+ exchanger 3 (NHE3) antagonist] decreased JHCO3– and changed the stimulatory effect of ANG-(1–7) to an inhibitory one but did not alter the inhibitory action of ANG-(1–7). In SHR, the control JHCO3– was 2.04 ± 0.13 nmol·cm–2·s–1 (n = 56), and A779 and/or losartan reduced the flow. ANG-(1–7) at 10–9 M increased JHCO3–, and ANG-(1–7) at 10–6 M reduced it. The effects of A779, losartan, and S3226 on the JHCO3– were similar to those found in WKY rats, which indicated that in SHR, the ANG-(1–7) action on the NHE3 was via Mas and ANG II type 1. The cytosolic calcium in the WKY or SHR rats was ~100 nM and was increased by ANG-(1–7) at 10&ndash...
Source: AJP: Renal Physiology - Category: Urology & Nephrology Authors: Tags: RESEARCH ARTICLE Source Type: research