Developmental changes of trypsin-like protease activity in the submandibular glands of male and female young growing rats

Fluid and protein secretion by the submandibular glands of weanling rats in response to various agonists

Secretion of fluid and protein by the submandibular glands of 25-day-old rats was investigated by stimulation with 22 sialogogues classified into five categories, four cholinergic, five beta 1-, seven alpha 1- and three alpha 2-adrenergic, and three peptidergic, at optimal doses. For fluid secretion, cholinergic and peptidergic agonists were the most powerful, whereas the beta 1- and alpha 1-adrenoceptor agonists were the most effective for the concentration of protein among the five categories, except for methoxamine. For total output of protein, the beta 1- and alpha 1-adrenoceptor agonists and pilocarpine were the most powerful among the 22 agonists, except for methoxamine and norephedrine. Cholinergic, peptidergic and alpha 2-adrenergic agonists among the five categories were less effective for protein secretion, except for pilocarpine. For the specific activity of esteroprotease, methoxamine and oxymetazoline, as alpha-adrenoceptor agonists, were the most powerful among the 22 agonists. Thus fluid and protein secretion evoked from the submandibular glands of weanling rats in response to a wide variety of agonists are similar to those of adult rats.

Changes in protein secretion by rat submandibular glands in response to isoproterenol, alpha-methylnoradrenaline, and clonidine during post-natal development

We studied developmental changes in salivary volumes and proteins secreted by the submandibular glands of male rats at weekly intervals from two to ten weeks of age in response to the beta 1-, alpha 1-, and alpha 2-adrenoceptor agonists, isoproterenol (IPR), alpha-methylnoradrenaline (alpha-mNA), and clonidine (Clonid). The types of proteins in saliva samples were determined and compared by isoelectric-focusing electrophoresis with the Phast system in both the gradient pH -3.5-to-5 and pH-3.5-to-9 gels by means of silver staining. Salivary volume and protein concentration in saliva samples elicited by IPR and alpha-mNA were positively related to the weight of the submandibular glands up to six or seven weeks of age, whereas in saliva elicited by Clonid, no relation was found in the protein concentration [corrected]. The isoelectric-focusing electrophoretic patterns of proteins secreted by the glands in response to three stimuli were different from each other during post-natal development. Within one stimulation, differences were also observed at two and three weeks of age for Clonid, and from seven weeks of age for the three stimuli, respectively. The alpha-type proteins, but not the beta-type proteins, were very similar to those in extracts from glands of rats at seven weeks of age. Almost all of the alpha-type proteins, but not the beta-type proteins, reacted with antibodies to two proteases. We conclude that functional maturation precedes morphological maturation in the submandibular glands of rats.

Effects of prolonged duct ligation of the rat salivary glands on the activity of trypsin-like protease

The effects of ligation on body weight, protease activity and hair kynurenine content were observed. The body weights of parotid gland(PT)-ligated and of combined submandibular (SM)-, sublingual (SL)- and PT-ligated rats were much less than those of sham-operated controls. However, the weights of SM,SL-ligated rats were similar to those of controls. The activity of trypsin-like protease in the duct-ligated submandibular gland was significantly reduced to 0.3-0.7 per cent of that in controls. Protein concentration also decreased in the duct-ligated submandibular gland. Kynurenine content in the hair of duct-ligated rats was higher than that in controls.

Developmental changes in the volumes, protein, and some electrolyte concentrations of male and female rat submandibular saliva secreted in response to methoxamine and pilocarpine

Saliva secreted in response to methoxamine and pilocarpine was collected from the cannulated ducts of the submandibular glands of male and female rats at weekly intervals from two to 10 weeks of age. It was analyzed for volume and for concentrations of protein, potassium, calcium, and inorganic phosphate. Following the collection of saliva, the submandibular glands were removed and weighted. The wet weights of the glands increased substantially up to seven weeks of age and then reached almost plateau values in both sexes. The salivary volumes secreted in response to both agents in both sexes were positively correlated with the gland weights, except that after five to six weeks of age there was no correlation between gland weight and methoxamine-stimulated salivary volume. The concentrations of protein, potassium, and inorganic phosphate were inversely related to the flow rates only at relatively low rates of flow. The concentration of calcium was positively correlated with the protein concentration and was independent of the nature of the stimulus and of sex differences during postnatal development.

Assay of trypsin-like protease in rat submandibular saliva and gland

Trypsin-like protease activity was high in the submandibular gland, low in the pancreas, and absent in the liver, kidney and brain of adult rats. The alpha-sympathomimetic agent, norepinephrine, induced a marked secretion of the enzyme into submandibular saliva and the remaining protease activity within the gland decreased to about 64 per cent of control levels. Six peaks of protease activity, found by isoelectric focusing in intact submandibular glands, were also detected in the saliva of norepinephrine-stimulated rats. Isoprenaline also increased the protease activity in saliva, but far less so than norepinephrine. The parasympathomimetic agent, pilocarpine, had little effect on the secretion of the enzyme into saliva.

Effect of leupeptin, a protease inhibitor, on dopa decarboxylase and protease activities in homogenates of submandibular salivary glands from young rats

Dopa-decarboxylase activity was high at 2-3 weeks of age, low at 5-6 weeks, and very low in adult rats; protease activity increased with age. Trypsin-like proteases, which decrease dopa-decarboxylase activity, were detected in the gland and were inhibited by a protease inhibitor, leupeptin. High concentrations (20 mg/ml) of leupeptin increased dopa-decarboxylase activity in the glands of adult rats to the level found at 5-6 weeks of age. The low activity of dopa decarboxylase in adult gland may be due in part to endogenous proteases.