Effect of hydration states on thermoregulatory responses during exercise in rats

Relationship between parotid amylase secretion and osmolality in the gastric contents of rats fed a pelleted or liquid diet

The relationship between parotid amylase secretion and the osmolality in the gastric contents of rats fed a pelleted or liquid diet was investigated. In sham-operated rats fed a pelleted diet, amylase activity in the parotid glands decreased, amylase activity in the plasma increased, and there was strong amylase activity in the gastric contents. As a result, both reducing sugar concentration and osmolality in the gastric contents increased. In parotid duct-ligated rats, the feeding of a pelleted diet affected neither parotid nor plasma amylase activity and there was little amylase activity in the gastric contents; this resulted in decreased starch digestion. The amylase activity in the gastric contents of rats fed a liquid diet was lower than that of rats fed the pelleted diet. Both the reducing sugar concentration and osmolality in the gastric contents of rats fed the liquid diet were lower than those of rats fed the pelleted diet. However, both the reducing sugar concentration and osmolality in the gastric contents of rats fed the liquid diet were higher than those in the liquid diet itself. A small quantity of parotid amylase seems to effectively digest a large part of the starch in the stomaches of rats fed the liquid diet. These findings suggest that amylase secreted from parotid glands increases osmolality in the gastric contents via the production of reducing sugars from starch in rats when fed either pelleted or liquid diets.