BASAL SYNTHESIS OF HEAT-SHOCK-PROTEIN-70 INCREASES WITH AGE IN RAT KIDNEYS

The heat shock protein (HSP) system is a mechanism of cell defense ind uced by stress, constitutively expressed during basal conditions and e ssential to the maintenance of cellular integrity. Acutely induced HSP synthesis decreases with aging, but the effect of age on the basal ex pression of HSP70 has not been specifically addressed so far. The aim of this work is to study the age-dependent basal concentrations of HSP 70 mRNA in rat kidneys. In 8 young (2-3 months), 6 adult (6-11 months) and 6 old male Wistar rats (22-27 months), steady-state concentration s of HSP70 and gamma-actin mRNA and of rRNA were measured. Pentosidine was measured by HPLC. The basal, unstimulated HSP70 mRNA is increased in young and old rats compared with adult subjects [young: 182% of ad ult levels (100-299), old: 167% of adults (142-209); p < 0.005]. The a mount of pentosidine increases with age (young: 0.6 +/- 0.1, adult: 1. 65 +/- 0.15; old: 2.3 +/- 0.3 pmol/mg of protein; p < 0.0001). It seem s likely that different mechanisms are responsible for the increased H SP70 basal synthesis in both the young and old animals. The prevalence of anabolic activity can trigger the increased basal production of HS P70 in young rats. The accumulation of posttranslational modified prot eins, documented by pentosidine, can chronically enhance HSP70 synthes is in aged animals. The suppression of the synthesis of other proteins accompanying HSP-selective production might contribute to the impairm ent of specific cell functions in aging.