Intracellular concentrations of the salt gland of the herring gull Larus argentatus.

Attempts were made to measure intra- and extracellular concentrations in secreting and inactive salt gland tissue of the herring gull. 14C-labeled polyethylene glycol (mol wt 4,000) was used as a marker for extracellular fluid. Fluid separated by centrifugation at 36,000 g appeared by three independent criteria to represent primarily extracellular fluid. It could not, however, be fully ascertained if this fluid was mixed with a small amount of intracellular fluid. Therefore, intracellular concentrations were calculated from the concentrations in centrifuged fluid as well as from plasma concentrations. By either method it was found that secreting and inactive glands showed no difference in extracellular and intracellular fluid concentrations of Na, K, Cl and Ca. Secreting glands had lower intracellular water content and a higher intracellular Mg concentration than inactive glands. The absence of evidence for intracellular accumulation of Na and Cl ions in secreting glands suggests that active ion transport takes place across the apical rather than the basal and lateral membranes in spite of the fact that Na-K-activated ATPase is associated with the extensive infoldings of these plasma membranes.