Expression of apoptosis regulatory proteins in the skeletal muscle of tumor-bearing rabbits compared with diet-restricted rabbits

The mechanism of body weight loss in the tumor-bearing state is still uncle ar. In this study, we investigated expressions of apoptosis regulatory prot eins in the skeletal muscle,of tumor-bearing and diet-restricted rabbits, a nd tried to evaluate the differences between the two groups. The apoptotic index (AI) in the tumor-bearing group was 28.1 +/-2.84 on day 10. By day 20 , many more apoptotic cells were found (AI: 40.5 +/-3.20), but then after d ay 20 their numbers gradually decreased (AI: 9.67 +/-2.22 on day 30 and 0.9 3 +/-0.96 on day 40). By contrast, no apoptotic cells were detected in the diet-restricted group at any of the times examined. Bcl-2 immunoreactivity was either not detected at all or only weakly observed in both groups. By c ontrast, Bax expression increased gradually after implantation in the tumor -bearing group. Bax expression in skeletal muscle cell was graded '++' (mod erate) 10 days after tumor implantation, and '+++' (high) by day 20, in 2 o f the 5 tumor-bearing rabbits. After day 20, however, Bax immunoreactivity decreased continuously in the tumor-bearing group. By contrast, hardly any Bax-immuno-positive cells were detected in the diet-restricted group. These results suggest that loss of body weight in the tumor-bearing group is dif ferent from that in the diet-restricted group, and is related to apoptosis of skeletal muscles.