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The Thai Journal of Veterinary Medicine

Abstract

Experiments were designed to determine the nature of the electrical potential difference as well as transport of water and electrolytes across the turtle urinary bladder Damonia subtri juga. In sodium chloride Ringer's solution a transbladder potential difference between 30-90 mv, was observed the mucosal side was negative with respect to the serosal side. A net flux of acid occurred in the opposite direction. An active chloride pump was believed to exist along with the sodium pump and hydrogen pump, thereby contributing to the potential difference observed across the layer of epithelial cells. This is because: 1) Chloride-free Ringer's solution increased both the potential difference on the short circuit current while the net flux of acid was constant; 2) Chloride could be transported against its electrochemical gradient when a sodium-depleted solution was used and 3) Sodium- depletion of the bathing solution caused the potential difference to reverse in sign and reach a new steady value of about 10-30 mv., sometimes even in the absence of hydrogen transport. The rate of acidification of the mucosal solution by the bladder was independent of the variation in chloride or sodium concentrations. However, there was a marked reduction of water and sodium transports when the pH of the solution bathing the mucosa was changed from 7.4 to 4.0. But water and sodium transports were not affected when serosal pH was changed to 4.0 or when either the serosal or the mucosal pH was changed from 7.4 to 9.0. It was suggested that the specific sodium permeability channel at the mucosal membrane was interfered with by the hydrogen in the mucosal solution, thereby reducing the transmovement of sodium.

First Page

214

Last Page

214

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