Protein production and processing in young adult and aged rat submandibular gland cells in vitro

Protein production and processing were evaluated in vitro in dispersed submandibular gland cells from young adult (4-6 months) and aged (24 month) rats. A modest decrease (approx. 25%) in protein production (incorporation of radiolabeled amino acids into 10% CCl3COOH-insoluble material) was found with old cells in both continuous-pulse and pulse-chase studies. Also new protein processing, followed by gel electrophoresis and autofluorography of radiolabeled samples, showed specific, marked alterations in old cells. In particular a significant difference in the processing of a 225 000 molecular weight glycoprotein (likely the major rat submandibular mucin) was detected.