Exercise inhibits progressive growth of the Morris hepatoma 7777 in male and female rats

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Abstract
Male and female rats were either trained to swim for a 6-week period or they remained sedentary. Rats were implanted with Morris hepatoma 7777 after 3 weeks of swimming and were sacrificed after a further 3 weeks. Exercised rats of both sexes showed a significant reduction in tumour weight at sacrifice, compared with sedentary controls (p < 0.01). Similarly, when rats were first implanted with tumours and then placed on an exercise program of 3 weeks duration, tumour growth was also reduced (p < 0.05). These results suggest that the tumour may be sensitive to exercise at more than one point in its development. Tumour growth was inhibited to a similar extent whether the total swimming time was 10, 20, or 30 h over the 3-week period. Although sedentary, tumour-bearing rats were anorexic; both male and female rats showed significant improvement of appetite during the period of tumour growth, in response to exercise. Tumour implantation was associated with significant losses of whole body and muscle protein. The progression of this wasting was not significantly altered by exercise.Key words: Morris hepatoma 7777, cancer, tumour, exercise, skeletal muscle, cachexia, protein.