Secretion by the parotid gland of the sheep: the relationship between salivary flow and composition

Abstract

Alterations in the concentrations of sodium and potassium in saliva have been extensively studied and related to the external balance of these ions, and to the level of function of the adrenal cortex. Rather less interest has been shown, however, in the relationship between these concentrations and the degree of activity of the salivary glands manifested by altering rates of flow, and in factors influencing the salivary concentration of anions. Heidenhain (1878) showed an increase in the salt content of dogs' submaxillary saliva from 0-19 to 0-50% associated with an increase in flow from 0419 to 1V37

Salivary Electrolyte Concentrations and Electrical Potential Difference Across the Parotid Salivary Duct of Anaesthetized Sodium-Replete Sheep

“…Coats and Wright (1957) used electrical stimulation of the parotid nerve to alter the rate of salivary flow, which is another obvious difference· between those experiments and the present investigation. However for the following reasons this difference is unlikely to be the cause of the different results obtained:…”

“…Previous reports have indicated that the relation between salivary flow and chloride concentration tends to be rather unpredictable (Coats and Wright 1957;Kay 1960;Beal 1979). During stimulation of salivary flow rate by acetylcholine infusion, the concentration of chloride fell in five experiments and rose in three.…”

“…and throughout the experiments there were no changes in salivary Na + /K + ratio that could be attributed to increased aldosterone secretion. The mean salivary Na + /K + ratio calculated for the experiment presented as typical data by Coats and Wright (1957) was 12·7. Clearly, mineralocorticoid secretion and consequent transport of sodium and potassium by the salivary ducts of the sheep used by Coats and Wright were not at minimal levels, presumably because their animals were not sodium-replete and/or because aldosterone secretion was stimulated during their experimental procedure.…”

“…The sodium concentration of parotid saliva from sheep has also been reported to increase with increasing flow rate (Coats and Wright 1957). However, in more recent studies the sodium concentration of parotid saliva was found to be negatively correlated with salivary flow rate in conscious sodium-replete sheep and goats when flow rate was altered by a variety of procedures (Olsson 1976;Beal 1977Beal , 1979.…”

“…Clearly, barbiturate anaesthesia does not alter the relations between flow and composition of sheep parotid saliva and thus some other explanation must be sought for the difference in salivary flow-sodium concentration relations between the experiments of Coats and Wright (1957) and those of Beal (1977,1979). Coats and Wright (1957) used electrical stimulation of the parotid nerve to alter the rate of salivary flow, which is another obvious difference· between those experiments and the present investigation.…”