ONE OF THE manifestations of cystic fibrosis is failure to produce a normal hypotonicity in the sweat. This defect may be due to inability to retrieve sodium and chloride from a precursor fluid. It may thus be failure of a "sodium pump" mechanism for secreting sodium from the sweat gland lumen into the extracellular fluid.
Such a sodium pump mechanism has been investigated in the "salt gland" of the albatross and other marine birds.1 It has also been investigated in the electrolyte transport across erythrocyte membranes.2 The present study was undertaken to test the possibility that failure of this mechanism was involved in the defect of the sweat glands in cystic fibrosis. The mechanism in the avian salt glands and the erythrocyte membrane has been shown to be accompanied by a turnover of phospholipids as indicated by incorporation of radioactive phosphate, particularly into phosphatidic acid. This phosphatidic acid