Effects of furosemide on sodium content and transport pool in frog skin (Rana esculenta): comparison with vasopressin and ouabain.

The effects of ouabain, vasopressin, and furosemide on intracellular concentrations of total sodium([Na]) and potassium [K]), on exchangeable sodium ([Na]) and the sodium transport pool ([Nap]) were investigated in isolated short circuited skins of rana esculenta. Furosemide was added to the epithelial bathing solution, vasopressin and ouabain to the corial bathing solution. Results were compared with the amount of net sodium transport measured by short circuit current (scc). Ouabain reduces scc and increases [Na] and [Na]; [K] is decreased. The administration of vasopressin leads to a sharp increase of scc, combined with an enhancement of of [Na] and [Na]; [K] shows no significant change. [Nap] is significantly increased, too, and approximately to the same amount as [Na]. Furosemide causes an increase of scc, whereas a significant change of [Na], [Na] and [K] could not be detected. On the other hand, [Nap] was enhanced significantly. The results support the hypothesis that furosemide like vasopressin is acting by increasing the entry of sodium into the transport compartment of the active cell layer. The result is an increased transfer of sodium across the skin.