A mathematical model of amphibian skin epithelium with two types of transporting cellular units.

A computer model of ion transport across amphibian skin epithelium containing two types of cellular units, their relative number and sizes, and a paracellular pathway has been developed. The two cellular units are, a large Na+ transporting compartment representing the major epithelium from stratum granulosum to str. germinativum, and a small, Cl- transporting compartment representing the mitochondria rich cell. The cellular units both contain dissipative and active pathways according to the two-membrane model. The Na+ transporting unit includes a (Na+, K+, 2 Cl-) co-transport system in the inward facing membrane. The outward facing membrane of the Cl- transporting units contains a potential gated Cl- permeability. Effects of ion distributions and changes in gating variables on the time course of transepithelial voltage clamp currents and their steady states are analyzed. The model predicts communication between the two cellular units under open circuit conditions.