Short CommunicationEffect of age and hypoxia/reoxygenation on mRNA expression of antioxidative enzymes in rat liver and kidneys
Introduction
During lifetime the organism encounters a series of damages including those caused by radicals or reactive oxygen species (ROS: H2O2, O2−, OH,NO).
In the ‘Free Radical Theory of Aging’, the increased production of superoxide radicals and H2O2 as major causes of aging has been discussed in addition to changes in the defense mechanisms and decreased formation of ATP (Harman, 1994).
Hitherto, reports concerning age-dependent changes of parameters of oxidative stress are partly divergent due to different methodology, species, organs, and parameters studied (Amicarelli et al., 1997, Azhar et al., 1995, De and Darad, 1991, De la Asuncion et al., 1996, Dogru-Abbasoglu et al., 1997, Ji, 1993, Rao et al., 1990, Rikans et al., 1992, Sanz et al., 1997, Sohal et al., 1995, Tian et al., 1998).
There are also conflicting data with respect to the influence of hypoxia on these parameters and on radical release, due to different hypoxia times and varying O2 pressures applied. Few publications can be found on the effect of age on mRNA expression of antioxidative enzymes and particularly the effect of hypoxia and reoxygenation on the expression of these genes (Amicarelli et al., 1997, Azhar et al., 1995, Dobashi et al., 2000, Gasbarrini et al., 1998, Rao et al., 1990, Rikans et al., 1992).
The aim of the present work was therefore to study the effect of age and of a short-time isobaric hypoxia and reoxygenation on MDA as an indicator for lipid peroxidation and on two antioxidative markers (total SOD activity and GSH) in rat livers and kidneys. In addition, we have investigated the cellular response on the gene level by determining mRNA expression of different antioxidative enzymes.
Section snippets
Treatment of animals
Male Wistar rats of two age groups (6 and 22–25 months) were maintained under standard conditions (a daily schedule of 12 h light and 12 h darkness, food and water ad libitum). Hypoxia was induced by down regulating the environmental O2 pressure to 5–6 vol.% within 25 min before sacrificing. Reoxygenation with atmospheric O2 pressure was performed within 4.5 h. Animals were treated according to the national standards for humane care of animals and the study was approved by the Regierungspräsidium
Parameters of oxidative stress
Table 1 presents the results of parameters of oxidative stress in liver and kidneys. The activity of total SOD and the GSH content were significantly higher in the liver of young rats than in old ones. Unexpectedly, the concentration of MDA was significantly increased in the liver of the young control group compared to the old one.
Hypoxia resulted in a significant rise of MDA in young hypoxic livers and in a decrease of SOD in young hypoxic and reoxygenation groups, whereas SOD showed a rise in
Discussion
In general, a higher oxidative stress caused by either increased ROS generation or restricted antioxidative defense mechanisms is discussed in aging (Harman, 1994). The significantly lower SOD activity and GSH content in livers as well as kidneys of old animals and the significantly higher MDA concentration in kidneys of old rats (Table 1) confirm this assumption and are in agreement with other authors (Azhar et al., 1995, De and Darad, 1991, De la Asuncion et al., 1996, Rao et al., 1990, Tian
References (30)
- et al.
Aging and detoxifying enzymes responses to hypoxic or hyperoxic treatment
Mech. Ageing Dev.
(1997) - et al.
Decline with age of the respiratory chain activity in human skeletal muscle
Biochim. Biophys. Acta
(1994) - et al.
Single-method of RNA isolation by acid guanidinium thiocyanate–phenol–chloroform extraction
Anal. Biochem.
(1987) - et al.
Age-associated changes in antioxidants and antioxidative enzymes in rats
Mech. Ageing Dev.
(1991) - et al.
Lipid peroxidation and antioxidant enzymes in livers and brains of aged rats
Mech. Ageing Dev.
(1997) - et al.
Chemiluminescent real time imaging of post-ischemic oxygen free radical formation in livers isolated from young and old rats
Free Radic. Biol. Med.
(1998) - et al.
Effect of age on the expression of antioxidant enzymes in male Fischer rats
Mech. Ageing Dev.
(1990) - et al.
Age-dependent modifications in rat hepatocyte antioxidant defense system
J. Hepatol.
(1997) - et al.
Changes in the expression of superoxide dismutase and catalase as a function of age and dietary restriction
Biochem. Biophys. Res. Commun.
(1989) - et al.
Oxygen dependence of glutathion synthesis in hepatocytes
Toxicol. Appl. Pharmacol.
(1989)