Hepatic iron accumulation is not directly associated with induction of DNA strand breaks in the liver cells of Long-Evans Cinnamon (LEC) rats

Mild zinc deficiency and dietary phytic acid accelerates the development of fulminant hepatitis in LEC rats

BACKGROUND AND AIM

Restriction of copper intake delays hepatic copper accumulation in Long-Evans Cinnamon (LEC) rats, which are animal models of Wilson's disease. Involvement of zinc is suggested to develop hepatitis in the disease; however, this has not been clarified. The aims of this study were to investigate the effects of mild zinc deficiency on the development of hepatitis and to determine the relationship between the absorption and hepatic levels of copper, zinc and iron.

METHODS

Male LEC and F344 (wild type atp7b) rats were fed a low zinc, phytate-containing or control diet. The onset of hepatitis (Experiment 1), and absorptive rates of copper, zinc and iron and hepatitis indices in 4 weeks (Experiment 2) were observed.

RESULTS

The onset of fulminant hepatitis in LEC rats was much earlier in the low zinc and phytate groups (mean 94.6 +/- 2.74 days and 82.8 +/- 3.56 days old, respectively) than in the control group (136 +/- 2.11 days old) with worse hepatitis indices. Hepatic copper levels were much higher in LEC rats than F344 rats, but were not largely different among the diet groups without prominent changes in copper absorption. Hepatic levels and intestinal absorption of zinc and iron were lower in the phytate group than in the control group.

CONCLUSION

Mild zinc deficiencies caused by a low zinc or phytate-containing diet accelerate the onset of hepatitis in LEC rats without increasing copper absorption, and zinc and iron metabolism may be involved in the earlier onset of jaundice of LEC rats.

Inhibitory effects of trientine, a copper-chelating agent, on induction of DNA strand breaks in hepatic cells of Long-Evans Cinnamon rats

Effects of treatment with trientine, a specific copper-chelating agent, on accumulation of copper and induction of DNA strand breaks were investigated in Long-Evans Cinnamon (LEC) rats, an animal model for human Wilson's disease. Copper accumulated in the livers of LEC rats in an age-dependent manner from 4 to 13 weeks of age. When LEC rats were treated with trientine from 10 weeks of age, hepatic copper contents did not increase and were maintained at the same levels as those in 10-week-old LEC rats. When the amounts of DNA single-strand breaks (SSBs) were estimated by a comet assay, SSBs of DNA were induced in a substantial population of LEC rat hepatic cells around 8 weeks of age and the amounts of SSBs increased in an age-dependent manner from 8 to 15 weeks of age. When LEC rats were treated with trientine from 10 weeks of age, the observed number of cells with DNA damage decreased dramatically, suggesting that induction of SSBs of DNA was inhibited and/or SSBs were repaired during the period of treatment with trientine. The results show that treatment of LEC rats with trientine decreases the number of DNA strand breaks observed, although copper contents remain high in the liver.

Production of age-related DNA strand breakage in brain cells of senescence-accelerated prone (SAMP1) mouse

Amounts of DNA strand breaks were estimated by the proportion of cells without tails (PCWT) and the average lengths of tail momentum (ALTM) in comet images of tissue cells of senescence-accelerated prone (SAMP1) mouse and senescence-accelerated resistant (SAMR1) mouse. The PCWT and ALTM of brain cells from SAMR1 were unchanged from 4 to 15 months of age. In the case of SAMP1 brain cells, the PCWT decreased and the ALTM increased in an age-related manner from 8 to 15 months of age. In the cases of liver and kidney, the PCWT and the ALTM of both SAMP1 and SAMR1 cells showed constant values from 4 to 15 months of ages.