Submandibular salivary secretion in the cat and associated potassium movements: dependence on temperature and perfusate flow rate.

Abstract

Cat submandibular glands were perfused with Locke solution in a thermostated chamber and intermittently stimulated with 10(-5)M acetylcholine (ACh). In one series of experiments the perfusion pressure was varied within the range 90-60 mm Hg, and secretory flow rate, active K+-reuptake, passive K+-release, and resting and ACh-induced venous flow rates were measured. The ACh-induced secretory flow rate and the maximal K+-fluxes were related to the simultaneous ACh-induced venous flow rates. A proportionality was found between the maximal rate of ACh-induced K+-release and ACh-induced venous flow rates below 8 ml/min, while at higher flow rates the K+-release leveled off. The maximal rate of the post-stimulatory K+-reuptake increased proportionally to the ACh-induced perfusate flow rate throughout the range studied. The secretory flow rate was much less affected by changes in ACh-induced perfusate flow rate. In another series of experiments the gland temperature was varied within the range 12-37 degrees C, and the same parameters were measured. All parameters decreased with cooling being reduced to 50% of their 37 degrees C values at: 24 degrees C for secretion, 19 degrees C for K+-reuptake, and 14 degrees C for K+-release. It is concluded: that the rate of ACh-induced K+-release is limited by the ACh-induced perfusate flow rate (within the physiological range), the capacity of the K+-reuptake mechanism is at least one order of magnitude larger than the maximal rate of K+-reuptake in vivo, the marked temperature sensitivity of the secretory flow rate reflects the high complexity of the mechanisms involved.