Abstract
The perfusion experiments were performed with dog's submaxillary gland and the mechanism of salivary secretion and the initiation of the secretory potential were studied by means of the microelectrode technique. Results obtained are as follows:
1. The intracellular potentials were very sensitive to changes of K+ concentration in the perfusate. When K+ was raised over 13mM/l, the secretory potential completely disappeared, while the secretion was still observed. Even when Cl- in the perfusate was replaced completely by sulphate, the secretory potential remained pratically normal 15minutes after starting the perfusion, but the rate of salivary flow decreased.
Therefore, the secretory potential is not the causal factor of secretion, and it seems to originate from some other factor than the Cl- pump along the cell membrane of the gland acinus.
2. From the balance study, it was concluded that the gland lost K+ with the rate of about 14&Eq/g.gland/min. into the blood and saliva during the secretion, while it was restored into the gland from the blood after cessation of stimulation and the restoration was completed in 15min., Na+ and Cl- were retained in thegland tissue en route from the blood to saliva by stimulation, while they werecompletely driven out and then into the blood during the restoration of 15min. By analysis of the ionic concentration in the gland tissue, a similar ionic movement was observed. The K+ in the gland decreased during the salivary secretion, whereas the Na+ concentration increased.
3. It is clarified by the aid of GOLDMAN'S equation that the rate of potassium permeability to that of the other ions increased more markedly in the secreting state than in the resting state. Thus, the equilibrium potential which ismanifested by the increase of K permeability during the stimulation of the gland seems to account for the hyperpolarization of the intracellular potential of the gland acinus. The secretion of saliva is not necessarily concomitant with the hyperpolarization of the cell membrane potential, and should be explained by some other factor than the secretory potential. A possible mechanism of salivary secretion was suggested in the discussion.
