[Cyclosporin A inhibits the response of osmotic water permeability to antidiuretic hormone in toad's bladder and to angiotensin II and antidiuretic hormone in toad's skin]

Abstract

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 arginine-vasotocin (AVT) and to angiotensin II (Ang II) and AVT in isolated toad skin. CyA added to the dermal side of isolated toad skin or to the serosal side of toad bladder in concentrations of 0.42. 10(-6) M to 0.42. 10(-7) M had no effect on basal osmotic water permeability (Posm) but inhibited the 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 toad skin in concentrations of 0.42. 10(-6) M and 0.42. 10(-7) M. In toad bladder it could be demonstrated that the inhibitory effect 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 effect in the mammalian nephron.