Rat parotid gland amylase: evidence for alterations in an exocrine protein with increased age

The content of alpha-amylase, the major exocrine secretory protein from rat parotid glands, was studied in young adult and aged rat tissue. alpha-Amylase protein was determined with an enzyme-linked immunosorbent assay. This employed antisera, produced against alpha-amylase purified from young adult rats, but which recognized and precipitated alpha-amylase enzyme activity equally well from both age groups. The parotid gland content of alpha-amylase was reduced about 50% in aged rats. Furthermore, the percentage of total gland protein which was alpha-amylase was decreased about 40% in aged animals. The data suggest that a somewhat specific alteration in alpha-amylase production (synthesis and/or degradation) occurs in parotid glands from aged rats. In addition, alpha-amylase functional activity was followed. The specific enzyme activity (U amylase activity per mg immunoreactive amylase) was about 35% higher in extracts from aged rat parotid glands compared to that of young adult glands.