[Determination, using a piezo-impulse method, of iso-osmotic permeability of the apical membrane of epithelium]

A frog skin, mechanically held on the mucosal side separates two Ringer solutions. It is submitted to an hydrostatic pressure difference delta P varying between 2 and 120 mb. Water permeability P (delta P) delta pi = 0 is determined with a piezo-impulse method. The rapid variation of permeability within the 2-25 mb range indicates a reversible closing of the junctions. The limiting value Pisol for high delta P is the isoosmotic permeability of the apical membrane.