Effect of Sodium Restriction on Secretion of Sodium and Potassium in Human Parotid Saliva

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Abstract
The relation between the rate of secretion and the concentration of sodium and potassium in human parotid saliva has been studied in three women with uncomplicated essential hypertension before and after severe restriction of the dietary intake of sodium. In both phases of the study the concentration of sodium rose with increase of secretory rate, approaching a maximum value at rates of flow exceeding 1.5 ml/min. This maximum value averaged 81.5 ± 6.2 mEq/l. when the patients were fed 175 mEq of sodium/day and fell to an average value of 59.5 ± 8.0 mEq/l. when the dietary sodium intake was reduced to 4 mEq/day. The concentration of potassium was largely independent of the secretory rate in both dietary phases of the study, averaging 18.0 ± 1.1 mEq/l. when the sodium intake was high and rising to an average value of 26.2 ± 4.1 mEq/l. after sodium restriction. Thus, the most sensitive salivary index of electrolyte-regulating hormone activity proved to be the Na/K concentration ratio of parotid saliva at rates of secretion above 1.5 ml/min. The parotid gland was found to lag behind the kidney by more than a week in its full adaptive response to sodium restriction. Submitted on June 12, 1956