Differential changes of cAMP-dependent protein kinase activity and H-3-cAMP binding sites in rat hippocampus during maturation and aging

The cyclic AMP-dependent protein kinase (PKA) has been involved in the brai n aging process and recent papers have reported age-associated changes in e nzyme activity in rat brain. The present study was undertaken to assess sim ultaneously PKA activity and regulatory (R) subunit levels during maturatio n and aging. Five cohorts of rats of different ages were used, namely pups of 1 week and 3 weeks old, mature rats (2 months), postmature rats (1 year) and old rats (2 years or more). PKA activity and H-3-cAMP binding sites we re determined in cytosolic fractions of hippocampus. Results showed a low P KA activity in newborn rats which increased in mature and postmature rats a nd finally declined in old rats (ANOVA, P < 0.001). The maximum binding sit es (Bmax) of H-3-cAMP which measure the PKA R subunit levels were elevated in newborn rats and declined in mature and old rats (ANOVA; P < 0.001). It is suggested the changes in PKA R subunit levels reflect an adaptative role in maturing process, a role which is lost in aging phase. (C) 2001 Elsevie r Science Ireland Ltd. All rights reserved.