Tumour purine nucleotides and cell proliferation in response to exercise in rats

Voluntary physical exercise can delay the onset of anorexia and cachexia in tumour-bearing rats. A substrate deviation in the host which has been hypothesised as tumour burden is reduced despite an increase in food intake. Therefore, we determined the levels of purine nucleotides, the energy charge and the cell division rate in tumours from exercising animals in the postexercise period. Tumour content of purine nucleotides was analysed by HPLC. Tumour cell kinetics was studied by flow cytometry after incorporation of bromodeoxyuridine (BrdU) into DNA. Exercising animals demonstrated a 34.4% reduction in tumour volume (P < 0.05) but a 1.31-fold increase in energy charge in tumour tissue (P < 0.05). Labelling index (LI), DNA synthesis time (Ts) and potential doubling time (Tpot) were not significantly altered. These results suggest that the influence on tumour growth is closely related to the exercise period.