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

Angiotensin-(1-7) (Ang-(1-7)) increased osmotic water permeability in the i solated toad skin, a tissue with functional properties similar to those of the distal mammalian nephron. Concentrations of 0.1 to 10 mu M were effecti ve, 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 P D 123319 (1.0 mu M) fully inhibited the response to 0.1 CIM Ang-(1-7) but h ad no effect on the response to Ang II at the same concentration. The speci fic receptor antagonist of Ang-(1-7), A-779, was ineffective in blocking th e response to Ang-(1-7) and to frog skin Ang II. The ATI receptor subtype a ntagonist losartan, which blocked the response to frog skin Ang II, was ine ffective 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.