REGULATION OF RESPIRATION.—THE EFFECT UPON SALIVARY SECRETION OF THE INTRAVENOUS ADMINISTRATION OF LACTIC ACID, SODIUM LACTATE, AND HYDROCHLORIC ACID

Abstract

In the dog the secretion of the pilocarpinised submaxillary gland is increased by the intravenous administration of lactic and hydrochloric acids. With the latter the increase in secretion varies in duration and magnitude and is followed frequently by a decrease below the original level. Its effect is the same whether the sympathetic supply to the gland is intact or not.Both agents increase the submaxillary blood‐volume flow with the vago‐sympathetic intact, but the magnitude of this change seems insufficient to account for the increase in secretion though it might contribute to it. A similar increase in blood‐volume flow is produced after cutting the vago‐sympathetic.The increase in secretion produced by lactic acid is greater if the vago‐sympathetic has been cut.Sodium lactate, intravenously injected, decreases salivary secretion if the vago‐sympathetic is intact but increases it if the nerve is cut. It increases submaxillary blood‐volume flow in a like degree whether the vago‐sympathetic is intact or not.The differences in the effects of lactic acid and sodium lactate before and after section of the sympathetic supply to the gland suggest a central as well as peripheral control of salivary secretion. The lactate ions appear to be inhibitory to the central and augmentory to the peripheral mechanism of secretion.All three agents cause transient changes in blood‐pressure, and both of the acids always increase pulmonary ventilation, though the change is generally more transitory than the effect upon secretion. Sodium lactate has no effect upon pulmonary ventilation or decreases it. Again the effect is transient.It is believed that changes in the acid base equilibrium of the tissues and blood are an important factor in the effect upon secretion of lactic acid, of hydrochloric acid, and of sodium lactate. Coincident changes in blood‐volume flow probably affected the results, and some additional effect of the lactate ionis, such as their use as food material supplying energy for secretion, may be involved.The act of cutting the vago‐sympathetic, while the submaxillary gland was secreting at a constant rate under the continuous injection of pilocarpine, increased submaxillary blood‐volume flow sharply but decreased the rate of secretion. Possible mechanisms producing these changes have been discussed.