A method for measurements of hydraulic conductivity of biological membranes in vitro

The results of measurements of water flow across four isolated epithelial membranes (skin of frogs, colon of rats, parietal peritoneum and mesentery of rabbits) with hydrostatic pressure gradient as volume driving force have been presented herein. The membranes were mounted between two semichambers filled with Ringer or Hanks solution; the volume on both sides of the membrane was strictly controlled by photogauges coupled with microdosimeters. Transmembrane volume flow (Jv; nL x sec-1 x cm-2) induced by the hydrostatic pressure gradient (delta P; atm) was measured with the use of an electronic device connected with the photogauges, and with a computer which monitored values throughout the experiment. Hydraulic conductivity index (Lp) was calculated from the monitored values (Lp = Jv/delta P; in cm x sec-1 x atm-1). The index proved to be a characteristic property of each studied membrane. Effects of some factors thought to influence the permeability of the membranes were checked: Hypertonicity of medium bathing the frog skin and parietal peritoneum induced an increase of permeability, whereas addition of mercuric chloride diminished it in the frog skin, the mesentery and the colon. The elaborated method can be useful in further studies on water metabolism and on participation of various barriers in water epithelial transport processes.