Volumetric flow across frog skin "in vitro"

Volumetric flow Jv across a membrane depends on several variables, one of them being hydrostatic pressure difference ΔP which can be simulated by the osmotic pressure difference of an impermeant solute Δπi = ΔP. In the present communication we describe the dependence of Jv upon Δπi in sacs made with the leg skin of Rana esculenta bathed in phosphate Ringer pH 7 at 20 °C. The impermeant solute (sucrose) was added only in the external perfusing solution while the inside solution was changed after each flow measurement to avoid any significant composition change. Volumetric flow was measured gravimetrically as in the case of gall bladder.