Effect of chronic insulin administration on mouse parotid and submandibular gland function

Chronic (six-day) injection of insulin (im, 50 microM/animal) into BALB/c mice resulted in changes in secretory function, hypertrophy and hyperplasia of the parotid and submandibular glands. There were no significant changes in the flow rate or concentrations of proline-rich proteins, TGF alpha, or amylase in saliva when measured against constant protein levels. However, amylase enzyme activity and total saliva protein content were reduced when measured against constant saliva volume. In contrast, EGF synthesis and secretion from the submandibular gland was increased. Both the parotid and submandibular gland showed evidence of gland hypertrophy and increased rates of DNA synthesis as indicated by [3H]-thymidine incorporation in response to insulin treatment. Chronic injection of insulin did not effect the level of receptor in the plasma membrane of either gland.