Different effects of fractionated irradiation on potassium efflux and exocytotic amylase release

Irradiation of head-neck cancer influences the salivary glands with dryness and discomfort for the patients as a consequence. In the present study we used in vitro secretory models and morphological characterization of rat parotid gland. Irradiation was given as a 5-day schedule with total doses from 20 Gy to 45 Gy. Electrolyte secretion (86Rb as indicator for potassium) caused by noradrenaline was decreased in correlation to irradiation dose delivered compared to controlateral control glands 10 days following irradiation. Noradrenaline stimulated exocytotic amylase release was not at all affected, and there were no signs of quantitative morphological alterations following irradiation compared to control glands. The results indicate that there are differences in radiation sensitivity for the two different secretory processes in the salivary glands; the structures regulating electrolyte and fluid secretion seem to be more vulnerable to irradiation than those regulating exocytosis.