Partial dissociation between salivary secretion and active potassium transport in the perfused cat submandibular gland

Summary

Isolated cat submandibular glands were perfused with Locke solutions in a thermostated chamber. Passive loss of potassium and uptake of sodium was achieved either by increasing the permeability of the cell membranes by acetylcholine (ACh) or by inhibiting the sodium-potassium pump reversibly by cooling or by removal of extracellular potassium. Irrespective of the way by which the cells were potassium depleted and sodium loaded, re-establishment of normal conditions was sufficient to cause an active net uptake of potassium (probably coupled to net extrusion of sodium). However, while ACh-induced changes in intracellular concentrations of monovalent cations were accompanied by salivary secretion, virtually no secretion was observed when normal conditions were re-established after concentration changes caused by inhibiting the sodium-potassium pump. It is concluded that while the transport mechanisms responsible for the maintenance of the intracellular concentrations of monovalent cations undoubtedly is a (Na⁺−K⁺)-activated ATPase, the transport mechanism responsible for the formation of the primary saliva is probably of a different type, since it apparently is not directly activated by the intracellular sodium concentration.