The Secretion of Lithium in Human Mixed Saliva: Effects of Ingested Lithium on Electrolyte Distribution in Saliva and Serum

Abstract

Outlining some of the more salient findings of this investigation: 1. Lithium appears in both saliva and serum without showing any appreciable time transient (found in saliva as early as one hour after administration). 2. Lithium is present in saliva at concentrations approximately two times that found in serum, this ratio holding in different diagnostic categories and over a wide range of dosages. 3. A concentration gradient obtained between saliva-serum lithium suggests an alternative method for determining blood levels. 4. An apparent correspondence exists between elevated concentrations of lithium ion and time of clinical improvement in manic patients. 5. Manic patients showing clinical improvement may be divided into two groups with respect to lithium distribution, one showing decreased lithium levels after the mania breaks and not the other. 6. There is a positive dependency between the concentration of lithium and volume of saliva secretions in function of time. Lithium appears capable of shifting volume dependency from sodium to itself. 7. Chronic lithium administration reduces plasma sodium and increases saliva sodium with concomitant increase of the Na/K ratio of saliva. There is no significant overall alteration of the potassium electrolyte in either saliva or serum. 8. Potassium was found in saliva at levels 2—4 times its concentration in serum, whereas sodium showed serum concentrations 4-5 times that of saliva. These findings which correspond to normal physiological gradients for these ions were generally not significantly altered by the introduction of lithium. Lithium, then, can be said to resemble potassium and differ from sodium in that it concentrates higher in saliva than serum. 9. Sodium tends to follow a reciprocal relationship with lithium. This supports existing beliefs that lithium is capable of replacing sodium in various systems. 10. It has long been recognized that the secretion of sodium and potassium (and chloride) in saliva is the result of osmotic activity by the secreting glands under the control of the adreno-cortical axis. The present findings are discussed in regard to such hormonal influence. 11. It is proposed that human mixed saliva may be used as a meaningful investigational tool in studying the effects of lithium.