The measurement of oxidation-reduction potentials, pH, and oxygen tension in tumours

Abstract

By use of the apparatus and techniques described in the previous paper (Cater, Phillips & Silver 1957 a ) the oxidation-reduction potentials in Walker carcinoma and Jensen rat sarcoma have been investigated, and compared with those of rat muscle, lactating mammary gland, liver, testis and brain. The changes which occur during the treatment of mammary carcinoma in man and the dog are also described. Breathing oxygen caused a rise of oxidation-reduction potential and oxygen tension in all these tissues except Jensen sarcoma. Intravenous injection of 2-methyl-1:4-naphthohydroquinone diphosphate (Synkavit) caused a fall in the oxidation-reduction potentials of all these tissues, as did cysteine, glutathione and cysteinamine, except that cysteine caused a rise and not a fall in grey matter of rat brain. 220 kVp X-rays even in low doses (100 to 200r) caused a potential fall at platinum, palladium or rhodium electrodes. 0·4 MeV γ -rays from 192 Ir were equally effective. No X-ray effect was obtained with a gold electrode, and it is suggested that the fall of potential with platinum, palladium and rhodium electrodes was due to hydrogen generated by the radiation in the tissue fluid. No change in the pH or oxygen tension was observed during irradiation. The experiments indicate the presence in the tissues of some form of ‘redox’ buffering system.