Expression of alpha-amylase isozymes in rat tissues.

Gene expressions of alpha-amylase isozymes in rat tissues were analyzed by a reverse transcription-polymerase chain reaction (RT-PCR), followed by EcoRI digestion. This procedure is based on evidence that an RT-PCR product from mouse pancreas RNA is sensitive to EcoRI, but not the product from the salivary gland or liver RNAs. The method was applied to the analysis of alpha-amylase expression in rat liver after partial hepatectomy, in which a potent expression of pancreas type isozyme was observed. However, no expression of the pancreatic isozyme in the regenerating liver was found. We also analyzed the expression of alpha-amylase gene in several additional rat tissues. In intestine, stomach, testis and skeletal muscle, the corresponding PCR products were amplified, but few were detected in heart or spleen. Intestine and stomach expressed a pancreatic isozyme of alpha-amylase. Analyses of the alpha-amylase activity and protein indicated the presence of the enzyme in those tissues. Immunohistochemical analysis also indicated that the amylase proteins were specifically present in epithelial cells of rat intestinal mucosa. This is a convenient method for identification of alpha-amylase isozyme mRNA in rodent tissues.