Journal of Dental Research, Vol 69, 1500-1504, Copyright © 1990 by International & American Associations for Dental Research Online Journals
Effects of diabetes and insulin on alpha-amylase messenger RNA levels in rat parotid glands
S. K. Kim, L. M. Cuzzort, R. K. McKean and E. D. Allen
Research Service, VA Medical Center, Ann Arbor 48105.
Previous studies have shown that amylase levels are reduced significantly
in the pancreas and parotid gland of diabetic rats and that insulin
reverses this effect and increases the secretory protein levels. In the
pancreas, these changes in amylase protein levels are accompanied by
parallel changes in amylase mRNA levels. In the present study, the effects
of diabetes and subsequent insulin treatments on contents (per cell) of
amylase protein and its mRNA in parotid glands were compared in rats
rendered diabetic with an injection of a beta-cell toxin, streptozotocin
(STZ). Both amylase protein and its mRNA contents were reduced
significantly in diabetic rats, compared with control rats, and this
reduction was reversed following insulin injections of diabetic rats. In
insulin-injected diabetic rats, amylase protein contents increased before a
detectable increase in amylase mRNA levels was seen. The mRNA contents of a
non-secretory protein, actin, did not change during diabetogenesis or
subsequent insulin treatments. The reductions in parotid contents of
amylase and its mRNA in diabetic rats and the reversal of these changes by
insulin are similar to those changes that occur in the pancreas under the
same conditions. However, the magnitude of these changes in parotid glands
was much smaller than in the pancreas, and the effect of insulin on amylase
mRNA synthesis was not as immediate as in the latter gland.
