[Changes of three types in the secretory systems present in the rat submandibular glands during aging]

Changes of the three types, termed here as alpha, beta and gamma, in the secretory functions present in the submandibular glands (SMG) of male rats were observed throughout almost all animal lives from 2 weeks to 24 months of age, by measuring changes of the wet weights of the SMG, salivary volumes secreted, the concentrations of protein, calcium and inorganic phosphate, and the types of proteins secreted in response to alpha-methylnoradrenaline (alpha-mNA) for the alpha-type, isoproterenol (IPR) for the beta-type and clonidine (Clonid) for the gamma-type, volumetrically, colorimetrically, atomic absorption-pectrophotometrically and isoelectric focusing electrophoretically. The molecular weight, isoelectric point and some posttranslational variations of a purified protein were elucidated by SDS-polyacrylamide gel electrophoresis (PhastSystem), isoelectric focusing electrophoresis (IEF, PhastSystem) on gradient pH 3.5 to 5 gels and neuraminidase or alkaline phosphatase treatment. The localization in the SMG, the inhibitory effects on the BrdU incorporation of the cultured thymocytes and the adhesive properties to the acrylic resin plate of this antigen were also analyzed by the indirect immunofluorescence, IEF and protein detection methods. The wet weights of the SMG were substantially increased up to 3.5 months of age with a positive correlation to body weight, but thereafter it reached the plateau level up to 24 months of age, somewhat different from changes of body weight. The salivary volumes as well as the amounts of protein secreted in response to alpha-mNA, IPR and Clonid were positively correlated to the wet weights of the SMG throughout the animal life. The concentration of calcium in the three types of secretions was positively correlated to the protein concentration, whereas the concentration of inorganic phosphate was tended to be reversely correlated to the salivary flow rate with some exceptions throughout the animal life. The gamma-type of proteins was not greatly changed, whereas the alpha- and beta-types of proteins were greatly changed in some proteins quantitatively or qualitatively throughout the animal life.(ABSTRACT TRUNCATED AT 400 WORDS)