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Ingestion of large amounts of ethanol results in a variety of toxicological consequences of which reduced oxygen supply is a marked respiratory effect. Experimentation involving the in-vivo administration of ethanol to rats, identifies the formation of ferri-haemoprotein species and hydroxyl radicals in the liver. Our work on the in-vitro effect of ethanol on oxyhaemoglobin shows the formation of ferri-haemoglobin and the alpha-hydroxyethyl radical as an intermediate. The impairment of oxygen transport efficiency of haemoglobin may be a result of its oxidation to the non-functional ferrihaemoglobin form.

When aqueous solutions of the spin trap 5,5'-dimethyl-1-pyrroline-N-oxide (DMPO) are treated with hydrogen peroxide in the presence of either FeII or light, the hydroxyl radical adduct DMPO-OH is formed, with a characteristic 4 line ESR spectrum. When oxy- or metmyoglobin is added to such a system the initial yield and the halife of DMPO-OH are reduced, and at high myoglobin concentrations (about 0.1 mmol dm-3) DMPO-OH becomes undetectable. Using the stable nitroxide 2,2,6,6-tetramethyl-1-piperidinyloxy-N-oxyl (TMPO) for comparison it was found that neither hydrogen peroxide nor myoglobin alone caused a loss of signal, but together a marked loss of signal was induced. From the evidence of these and other experiments it was concluded that the DMPO-OH adduct reacts with hydrogen peroxide and myoglobin to give non-paramagnetic products, and hence that the use of the DMPO spin trap to detect hydroxyl or other active radicals in systems containing physiological concentrations of myoglobin may give misleading results.

The application of e.s.r. spectroscopy to the study of radicals formed by mechanical means (grinding, shearing, bending, cutting, etc.) is discussed. Two mechanisms are considered, one being the homolytic breaking of main-chain bonds in polymers, and the other being charge-transfer (tribo-electric effect). The former is thought to occur for high polymers whilst the latter may be important for certain inorganic materials especially ionic solids. Specific examples are given for the generation of radicals by cutting finger nails and by grinding bone. In both cases, well-defined e.s.r. spectra were obtained for which identifications are offered. Possible implications of the mechanical formation of radicals in bone are considered.