Submaxillary secretion in rats treated with guanethidine

The composition of final submaxillary saliva and of whole gland homogenates were compared in rats treated with 14 daily doses of guanethidine (20 mg/kg body weight) and in untreated controls after stimulation with pilocarpine (10 mg/kg) or carbamylcholine (50-100 mg/kg). A 44% reduction in the volume of saliva and elevations in the salivary concentrations of K+, Ca2+ and protein were found in the treated animals after pilocarpine stimulation. Similarly, a 25% reduction in salivary volume and elevations in salivary Ca2+ and protein concentrations were observed following stimulation with carbamylcholine. A less significant elevation in salivary K+ was seen after this secretagogue. The Na+ and protein contents, but not the K+ and Ca2+ contents, were found to be elevated in the glands of the treated animals in the resting (unstimulated) state. After stimulation with the two secretagogues, however, similar changes in glandular Na+ and K+ contents were found in the glands of control and treated animals. The glandular water content was also similar in both types of glands in the resting and stimulated states. It is concluded that a reduced salivary secretion, rather than supersensitivity, is observed in the rat submaxillary gland following chronic guanethidine administration. The drug treatment does not impair the glandular electrolyte changes that occur upon stimulation, but most likely impairs the release of protein from the gland and also transductal K+ transport. Both these effects may result from the depletion of sympathetic neurotransmitter caused by the guanethidine administration.