Angiotensin-(1-7) increases osmotic water permeability in isolated toad skin

Angiotensin-(1-7) (Ang-(1-7)) increased osmotic water permeability in the isolated toad skin, a tissue with functional properties similar to those of the distal mammalian nephron. Concentrations of 0.1 to 10 mu M were effective, with a peak at 20 min. This effect was similar in magnitude to that of frog skin angiotensin II (Ang II) and oxytocin but lower than that or human Ang II and arginine-vasotocin. The AT(2) angiotensin receptor antagonist PD 123319 (1.0 mu M) fully inhibited the response to 0.1 CIM Ang-(1-7) but had no effect on the response to Ang II at the same concentration. The specific receptor antagonist of Ang-(1-7), A-779, was ineffective in blocking the response to Ang-(1-7) and to frog skin Ang II. The AT(1) receptor subtype antagonist losartan, which blocked the response to frog skin Ang II, was ineffective in blocking the response to Ang-(1-7). The present results support the view or an antidiuretic action of Ang-(1-7) in the mammalian nephron.