Abstract

The diffusional water permeability of collecting ducts in vitro and the cyclic A.M.P. content of isolated papillae were measured after exposure to different concentrations of antidiuretic hormone, isoproterenol and noradrenalin. Antidiuretic hormone 25 mu units/ml. caused a 25% increase in diffusional water permeability. This response was not affected by isoproterenol (10(-6) M) or noradrenalin (2 x 10(-6) M). Antidiuretic hormone 100 mu unit ml-1 caused a 50% increase in diffusional water permeability which likewise was not altered by isoproterenol or noradrenalin. Isoproterenol (10(-6) M) and noradrenalin (2 x 10(-6) M) had no significant effect on basal levels of diffusional water permeability. Isoproterenol had no significant effect on the tissue concentration of cyclic A.M.P. concentration induced by antidiuretic hormone. Noradrenalin (2 x 10(-6) and 10(-4)) had no significant effect on basal cyclic A.M.P. concentration. However, noradrenalin inhibited the stimulation of cyclic A.M.P. induced by antidiuretic hormone. This effect was inhibited by phentolamine. This study suggests that catecholamines do not alter water handling by a direct action on the water permeability of the kidney but probably exert their action through an effect of A.D.H. release.