THE RELATION OF CHANGES IN SODIUM TRANSPORT TO PROTEIN-BOUND DISULFIDE AND SULFHYDRYL GROUPS IN THE TOAD BLADDER EPITHELIUM

¹ Department of Pharmacology, State University of New York, Upstate Medical Center, Syracuse, New York

Antidiuretic hormones were added to isolated toad bladder lobes. If the addition of hormone produced an increase in short-circuit current (SCC), the hormone also produced a highly significant decrease in cellular protein-bound disulfide groups (PBSS) with no significant change in protein-bound sulfhydryl groups (PBSH). There is a good qualitative and quantitative correlation between antidiuretic hormone-induced SCC and the reduction in PBSS. 3', l-Cycic adenosine monophosphate and aminophylline also produced an increase in SCC and a reduction in PBSS. However, with this group of substances, the decrease in PBSS is matched by an equivalent increase in PBSH. Other substances such as amphotericin B and aldosterone, which increase the SCC in the toad bladder, also cause a significant decrease in PBSS without a significant change in PBSH. The changes in SCC and PBSS show both qualitative and quantitative correlations. The results suggest that the sodium-dependent short-circuit current in the toad bladder may be related to a change in the disulfide concentration in the toad bladder epithelial cells. The altered disulfide concentration may represent a structural membrane change which is related to the changes in permeability of the cellular membrane to sodium ion.