CHLORIDE CONDUCTANCE AND INTRACELLULAR CHLORIDE ACCUMULATION IN MOUSE PEYERS PATCH ENTEROCYTES

1. Measurements of membrane potential, Cl‐ conductance and intracellular Cl‐, K+, Na+ and H+ activities have been carried out in the follicle‐associated epithelium of the mouse Peyer's patch to characterize further the physiological properties of antigen‐transporting M cells, enterocytes and intraepithelial lymphocytes. 2. Intraepithelial lymphocytes, identified in random impalements as a second negative jump in membrane potential (Vm), were found to have higher K+ and H+ activities, lower Na+ and Cl‐ activities and higher negative values for Vm than either of the other two epithelial cell types. Cl‐ activity in these cells was higher than that predicted from the Nernst equation. 3. M cells identified as having the first negative jump in Vm in impalements involving intraepithelial lymphocytes were unable to accumulate Cl‐. They also had a lower Vm than that found in apparently fully differentiated enterocytes. This Vm was partly depolarized at a low Cl‐ concentration. 4. Apparently fully differentiated enterocytes could be further divided into two populations depending on whether the Vm could or could not be partly depolarized by a low Cl‐ concentration. The mean Vm and intracellular Cl‐ activity of Cl(‐)‐sensitive cells, measured in high Cl‐ medium, were less than values found for Cl(‐)‐insensitive enterocytes. Cl‐ was only accumulated by enterocytes showing no depolarization at low external Cl‐ concentration. 5. The Vm of mature villus enterocytes was the same as that determined for Cl(‐)‐insensitive follicle‐associated enterocytes. Villus enterocyte Vm was not depolarized at a low Cl‐ concentration. 6. The present ability to distinguish two apparently large populations of follicle‐associated enterocytes having M cell‐like or villus enterocyte‐like properties is discussed in relation to current theories describing how M cells might be formed. The presence of a Cl‐ conductance in M cell enterocytes, the inability to accumulate Cl‐ and the maintenance of a low Vm could aid endocytosis of macromolecules across the apical membrane. © 1990 The Physiological Society