Transmembrane movement of water and electrolytes in turtle urinary bladder

Abstract

Experiments were designed to study the transport phenomena of the urinary bladder of the Damonia subtrijuga turtle. A transbladder potential difference (P.D.) was observed between 30-90 mV, mucosal (M) negative with respect to serosal (S) side, and a net flux of acid occurred from S to M. Cl - free Ringer's solution increased both P.D. and short circuit current while the net flux of acid and base was constant. Na depletion from the bathing solution caused the P.D. to reverse in sign and reach a new steady value of about 10-30 mV. It is concluded that an active Cl - pump also exists along with the Na + pump and H + pump. The rate of transport of sodium was markedly reduced when the mucosal pH was lowered to 4.0 but not affected when the serosal pH was similarily changed or when either the serosal or the mucosal pH was changed from 7.4 to 9.0. It was suggested that the specific sodium channel at the mucosal membrane was interfered with by the H + ion in the mucosa solution, thereby reducing the transmovement of sodium.