Long-term aerobic swimming training by rats reduces the number of aberrant crypt foci in 1, 2-dimethylhydrazine-induced colon cancer

ABSTRACT

We determined the effect of long-term aerobic swimming training regimens of different intensities on colonic carcinogenesis in rats. Male Wistar rats (11 weeks old) were given 4 subcutaneous injections (40 mg/kg body weight each) of 1,2-dimethyl-hydrazine (DMH, dissolved in 0.9 percent NaCl containing 1.5 percent EDTA, pH 6.5), at 3-day intervals and divided into three exercise groups that swam with 0 percent body weight (EG1, N = 11), 2 percent body weight (EG2, N = 11), and 4 percent body weight of load (EG3, N = 10), 20 min/day, 5 days/week for 35 weeks, and one sedentary control group (CG, N = 10). At sacrifice, the colon was removed and counted for tumors and aberrant crypt foci. Tumor size was measured and intra-abdominal fat was weighed. The mean number of aberrant crypt foci was reduced only for EG2 compared to CG (26.21 ± 2.99 vs 36.40 ± 1.53 crypts; P < 0.05). Tumor incidence was not significantly different among groups (CG 90 percent; EG1 72.7 percent; EG2 90 percent; EG3 80 percent). Swimming training did not affect either tumor multiplicity (CG 2.30 ± 0.58; EG1 2.09 ± 0.44; EG2 1.27 ± 0.19; EG3 1.50 ± 0.48 tumors) or size (CG 1.78 ± 0.24; EG1 1.81 ± 0.14; EG2 1.55 ± 0.21; EG3 2.17 ± 0.22 cm³). Intra-abdominal fat was not significantly different among groups (CG 10.54 ± 2.73; EG1 6.12 ± 1.15; EG2 7.85 ± 1.24; EG3 5.11 ± 0.74 g). Aerobic swimming training with 2 percent body weight of load protected against the DMH-induced preneoplastic colon lesions, but not against tumor development in the rat.