CONTRIBUTION OF VILLUS AND INTER-VILLUS EPITHELIUM TO INTESTINAL TRANSMURAL POTENTIAL DIFFERENCE AND RESPONSE TO THEOPHYLLINE AND SUGAR

A chamber design is described which permits isolation of villus or intervillus epithelium from proximal segments of Amphiuma intestine and measurement of the transepithelial potential difference (ψms) and short-circuit current (Isc) produced by each. In media containing Cl- and 10 mequiv./l HCO3- the villus generated a basal ψms of 0.8 mV (serosa negative) and Isc of 12 μA/cm2 while the intervillus ψms and Isc were not different from zero. Acetazolamide altered the villus ψms by 1.2 mV; the intervillus ψms by only 0.3 mV. Transepithelial gradients of HCO3- appeared to generate diffusion potentials across the intervillus but not the villus epithelium. The actively transported sugar galactose elevated ψms by 0.6 ± 0.1 mV in the intervillus epithelium and by 1.5 ± 0.2 mV in the villus epithelium for a response ratio ( 0.6 1.5) = 0.4. The response ratio for valine was 0.3. In contrast, the response ratios for theophylline (0.7) and cyclic AMP (0.7) were significantly higher. These observations indicate that the entire epithelium is responsive to theophylline and cyclic AMP while Na+-dependent solute transport and the basal electrogenic ion transport processes are primarily functions of the cells lining the intestinal villus. © 1979.