EFFECT OF VASOPRESSIN ON THE PERMEABILITY OF NON ELECTROLYTES ACROSS THE SKINS OF RANA-ESCULENTA AND BUFO-BUFO

Maximal doses of vasopressin increase the permeability of the skins of B. bufo and R. esculenta to urea, ethylene glycol, glycerol, erythritol, .beta.-alanine, leaving virtually unmodified that of mannitol and antipyrine. These results demonstrate that the response to vasopressin is quite different in amphibian skins as compared to the bladders. A careful analysis of the effects of vasopressin on non-electrolyte permeability as a function of their molecular weight demonstrates that hormone elicits the formation of pores with a diameter inferior to 4 .ANG.. Under vasopressin treatment the skins exhibit a selectivity for polyhydroxylated molecules as compared to urea and .beta.-alanine. This selectivity is not due to active or facilitated transport and is not impaired by phloretin or DTNB which selectively blocks the permeability of urea or ethylene glycol in erythrocytes. It is proposed that the site of such selectivity is located in other plasma membranes of the epithelium.