Parotid secretion of rubidium

Parotid secretion of rubidium has been studied and compared with secretion of potassium. Potassium is rapidly transferred by the duct cells of the parotid gland from the plasma to the saliva. The concentration in a series of two-drop saliva samples reaches a peak in about the sixth sample after which the concentration is maintained characteristically high. In contradistinction, other ions display a rapid decrease in concentration. Rb86 shows a curve similar to that of potassium. Potassium and rubidium respond identically to changes in saliva flow rate. At flow rates of 0.2 or 0.3 ml/min. the concentration of both ions in the saliva is approximately twice that of the plasma. The S/P ratio progressively increases with decreasing flow rates reaching a maximum of about 8 at a saliva flow of 0.01 ml/min. Elevation of the plasma concentration of both ions evokes an increased saliva concentration. It is concluded that rubidium is transferred from plasma to saliva by the duct cells of the parotid gland and is transported by the same mechanism responsible for potassium secretion.