The effect of carbohydrates on the intestinal potentials of Cryptochiton stelleri.

1. The effect of various monosaccharides on the potential difference across the intestine of the invertebrate, Cryptochiton stelleri, was studied using an everted sac technique.2. D-Glucose, when present in the mucosal solution, increased the transmural potential across the anterior intestine but had no effect on electrical potentials across the posterior intestine.3. D-Galactose, when present in the mucosal solution, increased the transmural potential across the posterior intestine but had no effect on electrical potentials across the anterior intestine.4. D-Fructose and D-mannose, metabolizable but non-transported sugars, increased anterior intestinal potentials but not posterior intestinal potentials.5. 3-O-methylglucose, an actively transported (across the anterior intestine) but non-metabolizable sugar, did not alter potentials across either the anterior or posterior intestine.6. The addition of D-glucose to the serosal solution increased anterior intestinal potentials, but the serosal addition of D-galactose did not affect posterior intestinal potentials.7. NaF, phlorizin and anoxia prevented the increase in potential across the anterior intestine and phlorizin (10(-4) but not 10(-6)M) and NaF but not anoxia prevented the increase in potential across the posterior intestine.8. It was suggested that the effect of glucose on anterior intestinal potentials was a metabolic effect, whereas the effect of galactose on posterior intestinal potentials was related to the active transport of that sugar from mucosa to serosa.