In traditional Chinese herb medicine, Alismatis rhizoma has been used in treating edema, inflammation and increasing urine flow. Mechanism of Alismatis rhizoma¡¦s effect on these functions has not been elucidated. Since diuresis has been considered closely related to the reabsorption of sodium ion via the epithelium of tubule and collecting duct in kidney, we suspected that Alismatis rhizoma may influence transportation of salt and water. The measurement of short circuit current ( Isc ) has been used widely to estimate the ion transportation between mucosal and serosal side of epithelium. In the present experiment, we used the voltage ¡V clamp technique to demonstrate the effect of Alismatis rhizoma¡¦s extracts ( ARE ) on Isc and sodium ion conductance in frog skin. Our result showed that in control stage, the potential difference ( PD ) of frog skin is 64.81 ¡Ó 2.44 mV, the Isc is 59.82 ¡Ó 3.58 £gA / cm2 and the conductance is 1.09 ¡Ó 0.18 £gA / cm2 / mV. After ARE was applied to mucosal side of the frog skin, its Isc decrease from 62.63 ¡Ó 5.31 £gA / cm2 to 47.92 ¡Ó 5.41 £gA / cm2, which could further go down to 3.36 ¡Ó 1.06 £gA/cm2 by adding amiloride. Treating serosal side of frog skin with ARE decreased approximately 10% of its Isc. No apparent changes in conductance were observed by adding ARE to mucosal ( 0.98 ¡Ó 0.24 £gA / cm2 / mV ) or serosal side ( 0.96 ¡Ó 0.23 £gA / cm2 / mV ). Adding L-arginine ( the precursor of nitric oxide ) to the serosal side of the skin epithelium elevated the Isc for 17.10 ¡Ó 9.30 £gA/cm2. This effect can be inhibited by applying ARE or NG-L-nitro-arginine methyl ester ( L-NAME, NO synthase inhibitor ) before application of L-arginine. In summary, Alismatis rhizoma could affect Isc on both mucosal and serosal sides of the frog skin. Its effect on lowering Isc was more obvious when applied to the mucosal side than to the serosal side. The ARE may exert its effect on mucosal side by affecting amiloride¡Vsensitive sodium channel and on serosal side by affecting the NO signal transduction pathway.