Journal of Dental Research, Vol 71, 1885-1890, Copyright © 1992 by International & American Associations for Dental Research Online Journals
Effects of sialagogues on ornithine decarboxylase induction and proto-oncogene expression in murine parotid gland
M. Kawano, A. Ueno, Y. Ashida, N. Matsumoto and H. Inoue
Department of Biochemistry, School of Dentistry, University of Tokushima, Japan.
The mechanism of a sialagogue-induced increase in ornithine decarboxylase
(ODC) activity and the expressions of proto-oncogenes in murine parotid
gland were investigated by use of isoproterenol (IPR), carbachol (CC), and
methoxamine (MTX). The results were as follows: (1) The three sialagogues
had similar effects on the parotid in vivo (mouse parotid after a single
injection of IPR) and/or in vitro (rat parotid explants cultured on
siliconized lens paper floating on 199 medium containing IPR, CC, or MTX),
the order of their effectiveness being IPR > CC > MTX. (2)
Northern/dot and Western blot analyses revealed that the sialagogues
elevated the steady-state levels of ODC mRNA and ODC protein to maxima at
two h and six h, respectively, after stimulation. The increases were
roughly proportional to those in ODC activity, suggesting that
sialagogue-dependent enzyme induction is regulated at the transcriptional
level. (3) The mRNAs of four of nine proto-oncogenes examined showed
sialagogue-dependent increases to maxima at 30 min (c-fos) or 60 min
(c-jun, c-myc, and c-src) after the beginning of stimulation. These
increases were all transient, with the levels returning to the control
values (without sialagogue) within 60 min. (4) The IPR-dependent elevations
of ODC activity and the mRNAs of ODC, c-fos, and c-jun were inhibited by
monensin, but not by polymyxin B. On the other hand, the CC-dependent
increases in these parameters were inhibited by polymyxin B but not by
monensin.(ABSTRACT TRUNCATED AT 250 WORDS)
