Compartmental analysis of Na efflux across ileum mucosal membrane.

A new tracer analysis technique has been developed for efflux from a three compartment series system. With this technique, results are based on pools contributing to efflux and not on total tissue pools. The use of this technique is illustrated in a study of Na efflux across the luminal membrane of rabbit ileum. Na efflux was described by two exponentials with half-times of 1.78 min and 13.5 min. The fast component, with a flux of 68.0 mumoles/h cm2 and a calculated Na concentration of 166 mM, was identified as an extracellular compartment. The slow component, with a flux of 13.2 mumoles/h cm2 and Na concentration of 86 mM, was identified with efflux across the mucosal membrane of epithelial cells.