Journal of Dental Research, Vol 63, 1022-1027, Copyright © 1984 by International & American Associations for Dental Research Online Journals
Effect of substance P on exocrine secretion by rat submandibular gland cells
N. Fleming, P. T. Bilan and K. W. Graham
The effects of the undecapeptide, substance P(SP), on the secretion of
mucin and proteolytic enzymes from dispersed cells of the rat submandibular
gland were studied. The peptide, at a concentration of 1 X 10(-7) M,
stimulated the release of 31.9 +/- 3.0% (mean +/- SEM) of intracellular
mucin over 40 min, compared with 12.5 +/- 1.5% in untreated controls (p
less than 0.01). This effect was duplicated by the homologous peptides,
physalaemin, and eledoisin-related peptide. Substance P action was not
affected by pre-incubation of cells with phentolamine or propranolol and
was therefore independent of adrenergic stimulation. Furthermore, SP did
not enhance the intracellular concentrations of cyclic AMP or cyclic GMP,
confirming that cyclic nucleotides were not involved in its
stimulus-secretion coupling mechanism. The isoproterenol-stimulated
secretion of mucin from dispersed cells was reduced to 75.7% of the normal
response (p less than 0.01) after a brief exposure to SP. This inhibitory
effect was probably mediated by intracellular events rather than by direct
effects on cell surface receptors. However, mucin release after treatment
with SP followed by norepinephrine (NE) was 161% of that caused by NE alone
(p less than 0.01) and may reflect an additive response to the independent
stimulation of SP and NE receptors. Substance P and related peptides had no
effect on arginine esterase secretion in the experimental model, although a
response was elicited by alpha- and beta-adrenergic agonists. It is,
therefore, proposed that serous cells of the granular convoluted tubule in
the rat submandibular gland lack substance P receptors.
