Induction of a specific (LM) protein in the submandibular gland of the rat by repeated amputation of the lower incisor teeth.

Chronic administration of the beta-adrenergic agonist isoproterenol (IPR) leads to marked hyperplastic/hypertrophic enlargements of the parotid and submandibular glands in rats and mice with concomitant changes in the composition of both the glands and the saliva. Conspicuous among the alterations of the submandibular saliva is the appearance of a 13,000 Mr protein, termed LM (large mobile) protein. Repeated amputation of the lower incisor teeth also causes enlargements of the major salivary glands in rats. In this study, we have compared the enlargements of submandibular glands of rats produced by IPR administration or teeth amputation with respect to the relative levels of the LM protein in gland extracts and saliva. Administration of IPR-HCl (40 mg/kg) twice daily for 5 days or amputation of the lower incisor teeth 3 times a week for 3 weeks resulted in a 2.2-fold increase in the weight of the submandibular gland. Amputation for one week led to a 1.4-fold increase in gland weight. Double immunodiffusion in agar antibodies against the purified LM protein gave a single precipitin line with gland extracts and saliva of IPR-treated and teeth-amputated rats, indicating immunological identity of the reacting antigens. No precipitin lines were seen with gland extracts or saliva of untreated rats. Immunoblots of pooled saliva obtained from IPR-treated or teeth-amputated rats revealed a single protein band of the same electrophoretic mobility in SDS-polyacrylamide gels when stained using anti-LM antibodies. The relative concentrations of LM protein in gland extracts and saliva were measured by a solid-phase enzyme-linked immunoabsorption assay using antibodies against the purified LM protein.(ABSTRACT TRUNCATED AT 250 WORDS)