Abstract
The enzyme activities of endogenous xanthine dehydrogenase (XDH) and xanthine oxidase (XO) have been measured in 10 different types of mouse tumour and seven normal tissues. The conversion of XDH to XO has been observed in two tumour types upon the prolonged clamping off of the blood supply to the tumours. It is proposed that a similar conversion might also occur naturally in chronically hypoxic cells and that the ratio of the XO activity to the combined XO + XDH activities (%XO activity) could well serve as a marker for tissue hypoxia. A qualitative relationship exists between the %XO activity and literature values of the hypoxic fraction for some tumours measured by radiobiological assays. The influence of tumour size (about 0.2-1.8 g) on %XO activity is presented for all 10 tumours as well as %XO activity determinations for four of the normal tissues.
Highlights
MethodsTen different mouse tumours and seven normal tissues were used in this study
There may well be a large variability between patients and factors such as size and growth rate of the tumour might influence the size of a possible hypoxic fraction
There is strong radiobiological evidence that hypoxia exists in a range of animal tumours but estimations of their hypoxic fraction often vary widely with the assay method employed (Moulder & Rockwell, 1984)
Summary
Ten different mouse tumours and seven normal tissues were used in this study. Into 12-16-week-old CBA/Gy f TO or WHT/Gy f TO mice by injection of a crude tumour cell suspension subcutaneously on to the rear dorsum. Tumours were selected at sizes ranging from about 5 to 13.5mm mean diameter (0.2-1.8g) and excised immediately after killing the mice by neck luxation. Tumour samples (and normal tissues) were placed in vials containing previously ice-cooled buffer solution and maintained at 0-4°C before and during extraction of the enzymes. The buffer solution consisted of potassium phosphate 0.05 M, pH 7.4), sucrose (0.25 M), sodium salicylate (1 mM) and EDTA (0.3mM)
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