Effect of dietary soy protein on serum lipid concentrations during the growth of MCA-induced tumors in Fischer 344 male rats
Harris, Andrea D.
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Eighty male, Fischer 344 rats weighing 210-220 grams (9 weeks old) were randomly assigned to either a 20% casein-based (C) or a 20% soy protein-based (S) diet with 40 rats per dietary group. One week later, one half of the rats in each dietary group were implanted with a piece (2 mm3) ofMCA-induced sarcoma (T) and the other half of the rats were sham-operated (N). Ten rats in each subgroup (CT, CN, ST, SN) were killed at 1 0 days and the remaining 1 0 rats were killed at 20. days after implantation. The average tumor growth of the rats were not statistically different at either 10 days (CT=3.4 g; ST=2.5 g) or 20 days (CT=35 g; ST=43 g) after implantation. Tumor-bearing rats fed casein bad significantly higher HDL-cholesterol (HDL) than the other experimental groups at 10 days and 20 days after implantation. During the first 10 days of tumor growth, serum total cholesterol (TC) concentrations were significantly higher in animals fed casein (56.1 mg/dl) in comparison to animals fed soy protein (43.2 mg/dl) and in animals with tumors (54.8 mg/dl) in comparison to animals without tumors (44.6 mg/dl). After 20 days of tumor growth, casein fed rats with tumors had significantly higher serum total cholesterol than any of the other groups. There were no significant differences in triglyceride (TG) concentrations after 10 days of tumor growth. However, after 20 days of tumor growth~ TG concentrations were significantly higher in tumor-bearing rats regardless of the type of dietary protein. These data indicate an increase in the serum lipid levels during the growth of MCA-induced sarcoma.