Differences in blood glutathione levels of tumor-implanted or zinc-deficient rats

Previously we found that blood glutathione (GSH) levels were decreased in rats that were both zinc-deficient and tumor-bearing. In this study the separate effects of zinc deficiency and tumor were investigated. Young, male rats were pair-fed either a complete, control diet or a zinc-deficient diet, and some of each group were implanted intramuscularly (i.m.) with Walker 256/Ml carcinosarcoma. Then half of the tumor-implanted, zinc-deficient rats were repleted with zinc. All rats were killed 7 days after tumor implantation. Zinc deficiency was validated by poor growth, low food efficiency and decreased concentrations of zinc in liver, kidney and plasma. Relative to controls rats, the blood GSH level increased 21% as a result of tumor alone (P less than 0.005) and decreased 19% with zinc-deficiency alone (P less than 0.025). In rats that were both tumor-bearing and zinc-deficient, the GSH level was 16% higher than the controls (P less than 0.005). Zinc repletion of the tumor-bearing rats restored GSH levels to control values. These results indicate that the marked and opposite changes in blood GSH levels as a result of tumor implantation or of zinc deficiency occur by different mechanisms.