Journal of Dental Research, Vol 72, 897-906, Copyright © 1993 by International & American Associations for Dental Research Online Journals
The effects of tyramine on salivary flow rate and protein secretion by rat submandibular glands
A. Okina, S. Hidaka, M. Tashiro and K. Abe
Department of Oral Biochemistry, Fukuoka Dental College, Japan.
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 beta-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 alpha-blockers other
than yohimbine, and with most beta-blockers. The proteins secreted in
response to p-tyramine at all doses injected i.v. and i.p. were of the
alpha-type except with the lowest dose injected i.p. However, the
alpha-type was completely replaced by the beta-type in the presence of all
alpha-blockers except yohimbine, but not with beta-blockers, atropine, or
two enzyme inhibitors. Pargyline, a monoamine-oxidase inhibitor, but not
disulfiram, a dopamine-beta-hydroxylase inhibitor, affected all parameters
except the type of protein. Thus, p-tyramine may activate both the alpha 1-
and beta 1-adrenoceptors in the submandibular glands of rats directly or
indirectly.
