Atsuhito Okina

The Effects of p-Octopamine on Salivary Flow Rates and Protein Secretion by Rat Submandibular Glands

The effects of different doses of p-tyramine injected i.v. and i.p. on salivary flow rates and proteins secreted by the submandibular glands of rats were studied with and without various types of autonomic blockers and two enzyme inhibitors. The salivary flow rates and the amounts of protein secreted progressively increased with increasing doses injected both i.v. and i.p., whereas they were dramatically reduced with all autonomic blockers except the lowest doses of β-blockers, atropine, and yohimbine. Salivation in response to p-tyramine injected i.v. and i.p. was completely abolished by simultaneous injections of both prazosin and propranolol. The concentration of protein was not dose-dependent and was not reduced by yohimbine and phenoxybenzamine at almost all doses used. However, prazosin significantly increased the protein concentration. Protease activities were dose-dependent but were significantly reduced with a-blockers other than yohimbine, and with most β-blockers. The proteins secreted in response to p-tyramine at all doses injected i.v. and i.p. were of the a-type except with the lowest dose injected i.p. However, the a-type was completely replaced by the β-type in the presence of all a-blockers except yohimbine, but not with β-blockers, atropine, or two enzyme inhibitors. Pargyline, a monoamine-oxidase inhibitor, but not disulfiram, a dopamine-β-hydroxylase inhibitor, affected all parameters except the type of protein. Thus, p-tyramine may activate both the α1- and β1adrenoceptors in the submandibular glands of rats directly or indirectly.

The effects of clonidine and three 2-imidazoline derivatives on the secretion of protein and some electrolytes by rat submandibular and parotid glands

1. Three imidazoline analogues of clonidine were potent secretagogues for the parotid and submandibular glands at relatively high doses. 2. Salivation in response to clonidine was completely abolished by prazosin, phentolamine, phenoxybenzamine and dihydroergotamine. 3. The gamma-type of proteins was secreted in response to three of the analogues, whereas with p-aminoclonidine the alpha-type of proteins was secreted by the submandibular gland. 4. Albumin was specifically secreted by the submandibular gland in response to clonidine but not to isoproterenol or phenylephrine.

The effects of m-octopamine on salivary flow rates and protein secretion by rat submandibular glands

1. m-Octopamine given i.v. or i.p. was a potent sialogogue for rat salivary glands. 2. Salivation in response to i.v. m-octopamine was completely abolished by prazosin and phenoxybenzamine. 3. The alpha-type of proteins were secreted in response to all doses of i.v. and i.p. m-octopamine and these were converted into the beta-type with prazosin, but not with yohimbine. 4. m-Octopamine stimulated both alpha- and beta-adrenoceptors and was a much more selective alpha 1-agonist than was the p-isomer.

Abnormally High Levels of Cystatin S in Submandibular Glands, Saliva, and Gingiva of Plaque-resistant Rats

To identify salivary biomarkers of periodontal diseases, we used plaque-resistant and -susceptible rats as animal models. The levels of salivary cystatin S in saliva, salivary glands, and gingiva were tested in Nembutal-anesthetized young and adult plaque-resistant and -susceptible rats of both sexes with and without chronic treatment with isoproterenol. Isoproterenol was injected i.p. once a day for 4 or 6 consecutive days. Isoelectric focusing electrophoresis by the PhastSystem and the Western blotting method were used to separate different proteins and to identify a salivary cystatin S band in these samples. The expression of salivary cystatin S mRNA was also determined by the Northern blotting method. Depending upon the types of agonists, a few differences were observed in secretory functions between both strains of rats in both sexes, but the levels of salivary cystatin S in saliva elicited from the submandibular gland and in the extracts of the submandibular glands and gingiva were significantly higher in plaque-resistant rats when compared with those of plaque-susceptible rats in both sexes. However, no significant difference was seen between the strains after chronic treatment with isoproterenol. The N-terminal 26-amino-acid sequence of salivary cystatin S purified from submandibular saliva of plaque-resistant rats was identical with that purified from submandibular saliva of Sprague-Dawley rats subjected to chronic treatment with isoproterenol. The expression of salivary cystatin S mRNA was dramatic in the submandibular glands of the plaque-resistant rats and in the submandibular glands of Wistar rats subjected to chronic treatment with isoproterenol, but not in those of plaque-susceptible rats. These results suggest that salivary cystatin S might be a good biomarker in distinguishing between the two strains of rats and that its concentration is correlated with plaque resistance.

Fluid and Protein Secretion by the Submandibular Glands of Weanling Rats in Response to Cholinergic and Peptidergic Agonists at Various Doses

Fluid and protein secretion by the submandibular glands of 25‐day‐old rats were examined and compared in response to three cholinergic and four peptidergic sialogogues at various doses.

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

The present study was designed to determine whether the submandibular glands of weanling rats respond to α1-and β-adrenoceptor agonists in the same manner as glands from adult animals, to determine the doses of these agonists, which give the maximum responses, and using isoelectric focusing and twodimensional electrophoreses, to determine whether proteins in submandibular saliva are modified posttranslationally as they pass through the duct systems. All of the agonists used were potent sialogogues and were given i.p. over a wide range of doses. The volumes of saliva, the total output of protein and the relative activity of protease progressively increased with increasing doses of each agonist. The optimal dose of each agonist was neither low nor excessively high. The submandibular glands of weanling rats seem to be as fully developed for fluid and protein secretion as those of adult rats. In addition, no special protein was involved in saliva secreted by the submandibular glands of weanling rats at any of the doses of the various agonists used here. However, some proteins in submandibular saliva of 25-or 35-day-old rats, when compared with extracts of the submandibular gland, appeared to have been modified posttranslationally or degraded by proteases while passing through the duct systems of the submandibular glands of weanling rats.