The relationship between surface tension and release of rat jejunal brush border membrane hydrolases induced by sodium deoxycholate.

Rat jejunum was perfused in vivo with sodium deoxycholate concentrations ranging from 0.125 to 4 mM. The release of total protein and some brush border hydrolases (sucrase, maltase, leucine aminopeptidase and alkaline phosphatase) was followed as a function of both the time and the deoxycholate concentration. 1. Protein and enzyme release increased during deoxycholate perfusion only at concentrations greater than 0.5 mM. For each case, a plateau was reached at 2 mM deoxycholate. 2. After removal of deoxycholate from the perfusion fluid, the rate of protein and enzyme release dropped to the control levels. Following perfusion with 0.125 mM deoxycholate, however, there was a stabilizing effect so that the release rate of sucrase, maltase and alkaline phosphatase (but not of protein and leucine aminopeptidase) was smaller than that of the controls. 3. Protein and enzyme release was correlated with the deoxycholate-induced changes in surface tension. Significant increases in the release rates began between 0.5 and 1 mM deoxycholate when the surface tension fell below 50 dynes/cm. The plateau observed at or above 2 mM deoxycholate coincided with the stabilization of surface tension at 46 dynes/cm. 4. The maximum releasing effect also coincided with the critical micellar concentration of deoxycholate (1.5-2.5 mM).