To investigate the possible role of secretory granules in radiation-in
duced salivary gland dysfunction, rats were pretreated with isoprotere
nol (5 mg/kg intraperitoneally) to degranulate salivary gland acini, A
t maximal depletion, salivary glands were locally irradiated with a si
ngle dose of 15 Gy of X rays. Parotid and submandibular/sublingual sal
iva samples were collected before and 1-10 days after irradiation, The
lag phase, flow rate, concentrations of potassium and sodium, and amy
lase secretion were determined. Sham-treated, isoproterenol-treated an
d irradiated animals provided reference data. In the parotid gland, bu
t not in the submandibular gland, protection against radiation-induced
changes in flow rate and composition of saliva occurred after pretrea
tment with isoproterenol. Combining morphological data from a previous
study with data from the current study, it is suggested that improvem
ent of parotid gland function is attributed predominantly to a prolife
rative stimulus on acinar cells by isoproterenol and not to its degran
ulation effect, After pretreatment with isoproterenol, an earlier expr
ession of radiation-induced acinar cell damage leading to death was ob
served, followed by a faster tissue recovery, Thus the proliferative s
timulus on acinar cells may accelerate the unmasking of latent lethal
damage, resulting in the earlier replacement of dead cells by new, fun
ctionally intact cells. (C) 1995 by Radiation Research Society