Effect of methotrexate on protein and amylase secretion by rat parotid and submandibular salivary glands.

Saliva was collected from anaesthetized, methotrexate (MTX)-treated, pair-fed and control rats using either acetylcholine or bethanechol as secretagogue. Parotid saliva was analysed for protein and amylase content, and submandibular saliva for protein. Acetylcholine stimulation after MTX increased parotid protein output by 151 per cent, amylase output by 125 per cent and submandibular protein output by 229 per cent when compared to control values. There were no significant differences in either protein or amylase output between the control and pair-fed animals. With bethanechol, salivary amylase and protein secretion did not differ between MTX-treated and control animals. The significant increase in parotid protein and amylase output with acetylcholine was reduced by pretreatment with hexamethonium (5 mg/kg) or propranolol (5 mg/kg), but not by phenoxybenzamine (1 mg/kg). MTX did not increase the number or the dissociation constant of parotid beta-adrenergic receptors but did increase their number in the submandibular gland. Thus increases in protein and amylase output caused by acetylcholine MTX-treated rats may be the result of increased beta-adrenergic activity.