Although serum
amylase level is an important diagnostic factor in certain salivary and
pancreatic diseases, little information is available regarding the mechanism by which parotid
amylase reaches the circulatory system. The present study was carried out to investigate the relationship between parotid
isoamylase concentrations in blood serum and in parotid tissue in response to various stimuli. Wistar rats were fed with standard laboratory rodent chow; water was supplied ad libitum. In the first experiment, after a 16-h fasting, rats received either 5 mg/kg
pilocarpine or saline (control). In the second study, after fasting, half of the rats were fed for 1 h, the other half received no food. In the third experiment, the changes in serum and tissue
enzyme levels were monitored in freely fed animals during the peak-food intake phase, the first 2 h of the dark period.
Amylase concentration was determined by using
starch as a substrate. Pancreatic and parotid
isoamylase levels in serum were separated by gel-electrophoresis utilizing differences in ionic properties of the
isoenzymes. As expected,
pilocarpine strongly stimulated tissue
amylase discharge and serum
amylase elevation. Similar, but less pronounced changes were observed not only during refeeding of fasted animals, but also in nonfasted rats during their peak-feeding period. Our data suggest that pharmacological stimulation, such as with
pilocarpine or feeding in fasted state, as well as a mild stimulation of parotid function by spontaneous food intake during nonfasted state results in a decrease in parotid tissue
amylase activity and a proportional increase in serum levels of parotid
isoamylase.