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°C, and the same parameters were measured. All parameters decreased with cooling being reduced to 50% of their 37°C values at: 24°C for secretion, 19°C for K⁺-reuptake, and 14°C for K⁺-release. It is concluded: that 1) the rate of ACh-induced K⁺-release is limited by the ACh-induced perfusate flow rate (within the physiological range), 2) the capacity of the K⁺-reuptake mechanism is at least one order of magnitude larger than the maximal rate of K⁺-reuptake in vivo, 3) the marked temperature sensitivity of the secretory flow rate reflects the high complexity of the mechanisms involved.