ASSESSMENT OF BILE SALT NON-DEPENDENT FRACTION OF CANALICULAR BILE WATER IN RAT

Abstract

The bile-salt nondependent fraction of canalicular bile water was measured by the extrapolation to 0 of the regression line representing the relationship between bile flow and bile salt secretion. This extrapolation assumes that the secretion of bile salts, whatever their concentration, carries the same amount of water per molecule. In order to study this assumption, rats were depleted of bile salts by a bile fistula and infused with sodium taurocholate at rates varying from 30-500 m.mu.mol/min. Bile salt secretion was linear with bile salt infusion at any concentration. Values of bile flow and bile salt secretion were grouped according to bile salt concentration, and regression lines calculated. The slopes of the regression lines changes from 0.090 at bile salt concentrations below 10 mM to 0.012 at bile salt concentrations between 30 and 45 mM, (P < 0.001). The relationship between bile flow and bile salt secretion in the rat cannot be represented by only 1 regression line. The rate of secretion of the bile salt-nondependent fraction of canalicular bile water cannot be measured by the extrapolation of this single regression line.