Ciclosporine a inhibits the osmotic water flow response of isolated toad bladder to arginine-vasotocin and to angiotensin II and arginine-vasotocin in isolated toad skin

The purpose of the present study was to assess the effects of cyclosporine A (CyA) in the osmotic water flow response of isolated toad bladder to argi nine-va-sotocin (AVT) and to angiotensin II (Ang II) and AVT in isolated to ad skin. CyA added to the dermal side of isolated toad skin or to the seros al side of toad bladder in concentrations of 0.42. 10(-6)M to 0.42. 10(-7)M had no effect on basal os motic water permeability (Posm) but inhibited th e hormonal response to AVT in both membranes (AVT 10(-10)M in toad bladder. and 10(-8) to 10(-9)M in toad skin). CyA also inhibited the Posm response to Ang II (10(-7)M) in to,ld skin in concentrations of 0.42. 10(-6)M and 0. 42. 10(-7)M. In toad bladder it could De demonstrated that the inhibitory e ffect was reversible. CyA in concentrations of 0.42. 10(-6)M inhibited the Posm response of toad skin to theophylline (3.2. 10(-3)M) and to dibutyryl cyclic AMP (6.3. 10(-3)M) suggesting an effect distal to the generation of cyclic AMP These responses would support the possibility of a diuretic effe ct in the mammalian nephron.