Cysteine effect on toad bladder response to vasopressin, cyclic AMP, and theophylline

¹ Laboratory of Kidney and Electrolyte Metabolism, National Heart Institute, National Institutes of Health, Bethesda, Maryland

The increase in permeability to water and in short-circuit current of the toad's urinary bladder in response to 1 mU/ml of neurohypophyseal hormone was inhibited by 1 mm cysteine. The response to 10 mm theophylline was inhibited by as little as 0.1 mm cysteine. Cysteine or thioglycollate had no effect on the response to 1–4 mm cyclic-3',5'-AMP. The inhibitory effect of cysteine was evident under circumstances that would not be expected to cause appreciable reduction of hormone or theophylline; namely, low concentrations of cysteine were used, all solutions were well oxygenated, and there was no preincubation of hormone or theophylline with cysteine. The results are interpreted as indicating that cysteine acts at least in part by directly affecting intracellular processes rather than solely by chemical reduction of the hormone or theophylline in the bathing medium.

Key Words: oxytocin • antidiuretic hormone • adenosine-3',5'-monophosphate • adenyl cyclase

Submitted on July 23, 1963