Changes in activities of calmodulin-mediated enzymes in rat brain during aging.

Components of the calmodulin system, (i.e. calmodulin levels and activities of the following calmodulin-dependent enzymes: (Ca2+ + Mg2+)-ATPase, adenylate and guanylate cyclases, cyclic AMP and cyclic GMP phosphodiesterases, and Ca2+-dependent protein kinase) were studied in brains from rats of three different ages: 3 weeks old, 3 months old and 1 year old. With the exception of adenylate cyclase activity, all components measured were found to significantly decrease with increasing age. Adenylate cyclase activity was significantly higher in brains from the 3-month-old rats than in those from 3-week-old rats. Brains from year-old rats had adenylate cyclase activity that was intermediate between the two younger ages and was significantly different from both groups. The study provides evidence for important changes in the activity of this fundamental cell regulatory system in the central nervous system during the aging process.