TISSUE PROTECTION AGAINST OXIDATIVE STRESS

We used an enhanced luminescence technique to study the response of ra t tissues, such as liver, heart, muscle and blood, to oxidative stress and to determine their antioxidant capacity. As previously found for liver homogenate, the intensity of light emission (E) of tissue homoge nates and blood samples, stressed with sodium perborate, is dependent on concentration, and the dose-response curves can be described by the equation E = a . C/exp(b . C). The b value depends on the antioxidant defence capability of the tissues. In fact, it increases when homogen ates are supplemented with an antioxidant, and is correlated with tiss ue antioxidant capacity, evaluated by two previously set up methods bo th using the same luminescence technique. Our results indicate that th e order of antioxidant capacity of the tissues is liver > blood > hear t > muscle. The a value depends on the systems catalysing the producti on of radical species. In fact, it is related to the tissue level of h emoproteins, which are known to act as catalysts in radical production from hydroperoxides. The equation proposed to describe the dose-respo nse relation is simple to handle and permits an immediate connection w ith the two characteristics of the systems analysed which determine th eir response to the pro-oxidant treatment. However, the equation which best describes the above relation for all the tissues is the followin g: E = alpha . C/exp(beta . C-delta). The parameter delta assumes valu es smaller than 1, which seem to depend on relative amounts of tissue hemoproteins and antioxidants. The extension of the analysis to mitoch ondria shows that they respond to oxidative stress in a way analogous to the tissues, and that the adherence of the dose-response curve to t he course predicted from the equation E = a . C/exp(b . C) is again de pendent on hemoprotein content.