Osteogenesis bioassay and immunohistochemical and radioisotopic studies of a subunit of parotin, a parotid gland extract.

Bioassay data support the hypothesis that salivary glands participate in endocrine regulation of the development and maintenance of connective tissues. Resection of all three major salivary glands damages epiphyseal cartilages in young growing rats. A subunit obtained from parotin, an extract of bovine parotid glands, contains the active agent for the presumed endocrine function of salivary glands. Daily injections of 3 mg/rat of parotin or the subunit allow normal epiphyseal endochondral osteogenesis in salivary gland-deprived rats. The active agent appears to be secreted by the salivary acinar cells and resorbed through the striated ducts. Pancreatic islets and striated ducts of salivary glands share immunohistochemical activities for insulin, glucagon, and the subunit of parotin. Hyperglycemia and hypocholesterolemia occurred in intact rats given 1 to 5 mg/day of parotin for 30 days. These data together suggest endocrine function of the salivary glands and possible interactions between the pancreatic islets and salivary glands.