| Popis: |
Vasopressin exerts a unique effect on frog skin ( Ussing and Zerahn, 1951 ) and toad bladder ( Leaf, 1960 ; Bentley, 1958 ). Addition of the hormone to the serosal surface of the bladder results in an increase in the net flow of water along an osmotic gradient and a rise in both short-circuit current and potential difference (P.D.) across the membrane. These affects are specific for neurohypophyseal extracts, are reversible, and can be prevented by acidification of the bathing medium or the addition of certain sulfhydryl blocking agents ( Rasmussen et al , 1960 ). Vasopressin also stimulates the release of hydrocortisone from the adrenal ( Hilton et al , 1960 ) as does ACTH, and glucose from liver ( Bergen et al , 1960 ) as does epinephrine. Since the effects of the latter hormones involve the intermediacy of cyclic 3′,5′-AMP (C-AMP) and phosphorylase activation ( Sutherland and Rall, 1960 ; Haynes, 1958 ) the present studies were designed to test the hypothesis that vasopressin alters permeability by stimulating the production of cyclic AMP from ATP in toad bladder. Since conversion of C-AMP to inactive 5′ AMP is prevented by theophylline ( Butcher and Sutherland, 1959 ) the effect of theophylline on the toad bladder was also examined. |
