Abstract
α-amylase (EC.3.2.1.1) catalyzes the specific cleavage of α-1.4 glucan bonds in polysaccharides such as starch, and is produced by the pancreas (P-amylase) and the salivary gland (S-amylase). Stresses including radiation and major surgery are known to increase the activities of α-amylase in serum. However, the mechanism is not fully understood. Studies using Blue Starch as the substrate showed that X-ray irradiation of C3H/He mice increased the α-amylase activity in plasma at dose-dependent manner. A maximal activity of α-amylase was observed at 12 h after irradiation (about 3-fold). Non-denatured polyacrylamide gel fractionation of the plasma followed by starch-iodine staining showed that the S-amylase was dominant in mice and the activity was increased by irradiation, whereas that of P-amylase was not affected. On the other hand, irradiation failed to increase the activity or the protein level of α-amylase in human salivary gland cell lines HSG and HSY that were differentiated in Matrigel. Irradiation caused a decline in the pilocarpine-induced the flow rate of saliva and reduced the activity of α-amylase in saliva. Our results suggest that irradiation may not increase the synthesis but liberate α-amylase into blood via an increased permeability of cell membrane. Further studies are in progress.
