Electrical potentials and ion concentrations across the gut of Cryptochiton stelleri.

1. The electrical potential and concentration differences of Na, K, and Cl in the mucosal and serosal solutions of everted sacs of gut from Cryptochiton stelleri were determined.2. The parameters were used to determine if active ion transport was present in segments from the anterior and posterior intestine.3. The electrical potentials were of the order of 0.5 mV, serosa negative, in the anterior intestine, and 1 mV, serosa positive, in the posterior intestine. The potentials, although small, were significantly different from zero.4. The potentials of all segments responded to anoxia and incubation at different temperatures in a manner indicating that they were of active origin.5. Ions were accumulated against electrical potentials in some segments but did not respond to anoxia or incubation at different temperatures in a consistent fashion.6. It was concluded that active ion transport was present but no evidence for active transport of Na, K or Cl across the gut could be found.7. K leaked from the gut during incubation at non-physiological temperatures or during hypoxia and was removed upon restoration of physiological conditions.