[Circadian chronotherapy for Walker-256 of Wistar rat]

The tumor growth of Walker-256, 10(7) cells of which were implanted into Wistar rat's hindpaw s.c. were measured regularly at 7.00, A. M. and 7.00, P. M. The tumor growth ratios during day (TG-day) and night (TG-night) were 3.8 +/- 3.4%, 29.4 +/- 9.3%, (Tumor Vol < 250 mm3, p < 0.05), 9.6 +/- 4.4%, 30.4 +/- 8.1%, (250 mm3 < T. V. < 750 mm3, p < 0.05) respectively. After tumor vessels formed. TG-day and TG-night were 19.4 +/- 6.1%, 26.6 +/- 5.3%, (750 mm3 < T. V., p > 0.05) respectively. This data showed us circadian rhythms of the tumor growth of Walker-256 which didn't form tumor vessels. Walker-256 and body weight of Wistar rats given 5mg/kg/day of 5-FU p. o. at 7.00, A. M. (day therapy) or at 7.00 P. M. (night therapy) from the second day to the eighth day were 250.5 +/- 31.5 mm3 (n = 8), 62.8 +/- 55.8 mm3 (n = 8) (p < 0.05) (no treatment group: 1,616.0 +/- 321.0 mm3, n = 9) and 111.2 +/- 82.2 g, 156.3 +/- 3.1 g (p < 0.05) respectively. This method of therapy could be appreciated as the chronotherapy.