-METHYLGLUCOSIDE TRANSPORT BY THE GILL OF THE OYSTER OSTREA EDULIS

¹ Marine Division, Corvallis Environmental Research Laboratory, Environmental Protection Agency, Corvallis, OR 97330

The glucose transport system in the gill of Ostrea edulis was studied using -methyl[U-¹⁴C] glucoside. The same mobile carrier transported -methylglucoside (-MG) and D-glucose in the isolated gill. Unlike D-glucose -MG was not appreciably metabolized to CO_2. It was hypothesized that the mobile carrier is specific for the hydroxyl group at the C₃ position of D-glucose. Ouabain (0.1 mM) did not reduce -MG uptake, thus suggesting that Na⁺ transport was either via a ouabain insensitive pump or a ouabain sensitive pump inaccessible to ouabain dissolved in seawater, the external medium. Compounds capable of collapsing the transmembrane electrical potential reduced -MG uptake. Naphthalene, a compound known to hyperpolarize muscle cells, stimulated -MG uptake. Inner leaks via the mobile carrier were determined to be much greater than outer leaks. The results indicate that the glucose transport system in the oyster gill has many similarities to Na⁺-dependent transport of glucose in mammalian small intestines and proximal renal tubules. Naphthalene stimulation of -MG uptake is consistent with a previous study demonstrating naphthalene stimulation of glucose metabolism in gill tissue.