Peroxidase and kallikrein in atropine-resistant secretion of submandibular saliva on parasympathetic nerve stimulation in anaesthetized rats

Abstract

Flow of submandibular saliva and the constituents secreted during chorda-lingual nerve stimulation at 40 Hz (3 x 10 min) were studied after α- and β-adrenergic blockade, and in the absence (control) or presence of cholinergic blockade in anaesthetized rats. Peroxidase and true tissue kallikrein (rK1) were assessed to gain insight into the effects of the non-adrenergic, noncholinergic (NANC) transmitters on protein secretion by acini and granular tubules, respectively. From control glands there was an overall mean flow of 181 ± 15 μl g-1 min-1, with no significant differences between the three periods. Secretion from atropinized glands was approximately 20% of that from control glands in the first 10 min, decreasing progressively to approximately 6% in the final period. Protein outputs from control glands showed no significant differences for the three periods (0.23 ± 0.05 mg g-1 min-1). Protein outputs from atropinized glands were similar to controls in the first 10 min and then decreased significantly. Peroxidase output from control glands increased progressively (from 31 ± 7 to 243 ± 68 pmol dichlorofluorescein (DCF) g-1 min-1) but in saliva from atropinized glands the overall mean output was only 4.5 ± 0.8 pmol DCF min-1 ml-1, with a progressive decrease between samples. Outputs of rK1 from control glands were similar for all samples (20.6 ± 4.0 nmol AFC g-1 min-1), but there was a significantly smaller and decreasing output of rK1 from atropinized glands. In conclusion, NANC transmitters released from parasympathetic nerves during stimulation at high frequency appear to have little influence on the secretion of protein from rat submandibular acini and granular tubule cells when acting in isolation. This contrasts with their effects on amylase secretion from rat parotid glands under similar circumstances.