Effects of pentoxifylline and various methylxanthine derivatives on transepithelial water permeability of frog urinary bladder.

Theophylline, pentoxifylline and MIX (isobutyl methylxanthine) increase the water permeability of frog urinary bladder when added to the serosal side of the epithelium; this hydrosmotic effect is explained by an inhibition of adenylate cyclase. Both pentoxifylline and MIX exhibit an higher biological activity than theophylline. In contrast to theophylline, pentoxifylline and MIX stimulate the water permeability when added to the mucosal side of the epithelium; this probably results from a better penetration of these drugs into cells.