Change of membrane potential in rat urinary bladder epithelium treated with sodium L-ascorbate.

We previously showed that 5% sodium L-ascorbate (Na-AsA) in the diet promotes rat urinary bladder carcinogenesis, whereas 5% ascorbic acid (AsA) and 1% sodium chloride (NaCl) in the diet do not. In order to cast light on basic properties of these compounds regarding the rat urinary bladder, we examined membrane potential levels in the bladder epithelium of F344 rats treated with 5% Na-AsA, 5% AsA or 1% NaCl in the diet for 2, 4 or 8 weeks. Microelectrode measurement showed Na-AsA to induce hyperpolarization of the membrane potential, which was, however, lacking with AsA and NaCl from week 2 until the end of experiment. Thus a good correlation between the effects on membrane potential and tumor promoting activity could be established.