Transport mechanisms in the anterior intestine of Cryptochiton stelleri

The in vitro everted sac method of Crane and Wilson as modified by Lawrence was employed in the study of the basic transport mechanisms for salt, water, and organic nutrients, specifically glucose and 3-O-methyl glucose, in the anterior intestine of the marine invertebrate, Crytochiton stelleri. The parameters measured were the sodium flux, sugar flux, water flux, transmural potential, and pH. The experimental conditions imposed upon the tissue included ion replacement, in which one or more ions was replaced in the bathing medium, and the use of inhibitors, particularly anaerobiosis and 1 x 10[raised -6] ouabain. The results of these experiments seem to indicate that sodium ion is actively transported by the anterior chiton gut, and that this transport is ouabain sensitive and is inhibited by anaerobic conditions. The movement of potassium, chloride, and water is most likely passive. The active transport of glucose and 3-O-methyl glucose is dependent upon the presence of sodium. The negative potential across the anterior gut appears to be the result of the active transport of hydrogen ion from the serosal to the mucosal compartment. This transport is ouabain insensitive but is inhibited by anaerobic conditions. A model for the transport mechanisms in the anterior chiton gut encompassing these observations is proposed.