Electrochemical potential of calcium as index of intestinal permeability in rat and chicken.

The electrochemical potential of calcium between the serosal and the mucosal sides of the small intestine in both rat and chicken have been studied in vitro. Techniques to measure the Transmural Potential Difference and the Short-circuit Current Intensity have been used. Our results indicate that the permeability coefficient of calcium in rat intestine towards the serosal is sixfold over that towards the mucosal. In chicken intestine it is approximately of the same order on either side. The permeability coefficient is defined as the ratio delta Eexp/ delta Etheor, where delta Eexp stands for the difference, experimentally measured, of the electrochemical potential under two distinct conditions of calcium in the medium, and delta Etheor stands for its expected value under conditions of zero permeability.