HYDROGEN-PEROXIDE METABOLISM AND OXIDATIVE STRESS IN CORTICAL, MEDULLARY AND PAPILLARY ZONES OF RAT-KIDNEY

The cortical, medullary and papillary regions of rat kidney were evalu ated for a series of parameters related to hydrogen peroxide metabolis m and oxidative stress. The rates of oxygen uptake, prostaglandin synt hesis and malondialdehyde production by kidney slices were: 47, 0.003 and 0.051 mumol/h g wet wt., respectively, in cortex, 32, 0.023 and 0. 035 in medulla and 22, 0.034 and 0.007 in papilla. The activities of s uperoxide dismutase, catalase and glutathione peroxidase were: 144 +/- 16 U/g wet wt., 880 +/- 100 pmol/g wet wt. and 177 +/- 16 U/g wet wt. in cortex; 97 +/- 9 U/g wet wt., 550 +/- 50 pmol/g wet wt. and 142 +/ - 18 U/g wet wt. in medulla; and 23 +/- 2 U/g wet wt., 90 +/- 9 pmol/g wet wt. and 147 +/- 5 U/g wet wt. in papilla. Hydrogen peroxide stead y-state concentrations were 0.09 +/- 0.01, 0.07 +/- 0.01 and 0.08 +/- 0.01 muM whereas alpha-tocopherol content was 21 +/- 2, 23 +/- 1 and 3 4 +/- 3 mumol/g wet wt. and hydroperoxide-initiated chemiluminescence was 22 +/- 2, 33 +/- 2 and 14 +/- 1 cpm. 10(-3)/mg prot for cortex, me dulla and papilla, respectively. After 60 min ischemia-30 min reperfus ion hydroperoxide-initiated chemiluminescence and hydrogen peroxide st eady-state concentration increased by 30% and 60% in cortex and 80% an d 60% in medulla, whereas alpha-tocopherol content decreased by 30%, 5 0% and 2% in cortex, medulla and papilla, respectively. The reperfusio n/control ratio of hydroperoxide-initiated chemiluminescence and hydro gen peroxide steady-state concentrations in cortex and medulla indicat e the occurrence of oxidative stress after ischemia-reperfusion. The l ower sensitivity to oxidative stress found in papilla could be explain ed by the relatively high relationship of alpha-tocopherol content to hydrogen peroxide production rate in this sub-organ.