The role of the transbranchial potential difference in hyperosmotic regulation of the shore crabCarcinus maenas

Abstract

When isolated gills of the shore crabCarcinus maenas were bathed and perfused with identical solutions on both sides (50 % sea water), a spontaneous transepithelial potential difference (PD) of some millivolts (hemolymph side negative) was established. This PD is of active nature and requires the metabolism of the living cell, since it uses its own sources of energy in addition to organic nutrients offered in the flow of artificial hemolymph. Addition of sodium cyanide and dinitrophenole to bathing and perfusion medium resulted in reversible breakdown of PDs in a concentration-dependent mode. In posterior gills ofC. maenas, the potential differences were more negative compared to data measured in anterior gills of the same individuals. These results are correlated with higher specific activities of Na-K-ATPase in posterior gills. Experiments with triamterene indicate that sodium uptake inC. maenas is sensitive to this diuretic drug, when applied on the apical side of the epithelial cell. The results obtained show that active uptake of sodium from medium to blood across the gills is performed by a complex mechanism including participation of several basal and apical transport steps.