Induction after administering paraquat of heme oxygenase-1 and heat shock protein 70 in the liver of senescence-accelerated mice.

Age-associated changes in the induction of heme oxygenase (HO-1) and heat shock protein 70 (HSP70) after the administration of paraquat were investigated in the liver of senescence-accelerated mice (SAMs). The extent of HO-1 and HSP70 induced in response to paraquat decreased significantly with age, and the level of oxidized proteins increased with age. Moreover, the extent of induced HSP70 was lower in mice that were prone to accelerated senescence (SAMP1/(/)Fky) than in mice that were resistant to accelerated senescence (SAMR1/Fky) of the same age. These results suggest that an age-associated decline in the levels of HO-1 and HSP70 enhanced oxidative damage during the aging process. Age-dependent changes in HO-1 and in the levels of oxidized proteins were examined in SAMP1/(/)Fky. The accumulation of oxidized proteins was suppressed when HO-1 was induced, but increased markedly after the induction of HO-1 decreased. Free iron, the residuum from heme degradation, might mediate free radical production. The role of HO-1 is discussed in relation to the oxidative damage associated with age.