Effects of Iron Overload during Pregnancy on Oxidative Stress in Maternal Rats

Mi-Na Park; Yeon-Sook Lee

doi:10.4163/kjn.2011.44.1.5

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Park and Lee: Effects of Iron Overload during Pregnancy on Oxidative Stress in Maternal Rats

Research Article

Korean Journal of Nutrition

Korean Journal of Nutrition 2011; 44(1): 5-15.

Published online: 28 February 2011

DOI: https://doi.org/10.4163/kjn.2011.44.1.5

Effects of Iron Overload during Pregnancy on Oxidative Stress in Maternal Rats

Mi-Na Park, Yeon-Sook Lee

Department of Food and Nutrition & Research Institute of Human Ecology, Seoul National University, Seoul 151-742, Korea.

To whom correspondence should be addressed. (lysook@snu.ac.kr)

Received 25 October 2010 Revised 27 December 2010 Accepted 11 January 2011

Abstract

Although iron is an essential mineral, excess iron intake during pregnancy may increase oxidative stress in tissues. This study was conducted to investigate the effects of iron overload during pregnancy on iron status and oxidative stress in maternal rats. Ten week-old female Sprague-Dawley rats were mated with male rats. Non-pregnant (control) and pregnant rats were fed diets containing normal Fe (35 mg/kg diet), high Fe (350 mg/kg diet), or excess Fe (1,050 mg/kg diet) during pregnancy. Rats were sacrificed on pregnancy day 19. No significant difference in weight gain, diet intake, or litter size was observed according to iron intake levels. Furthermore, serum iron, hemoglobin, and hematocrit were not different among the rats administered the three levels of Fe both in the control and pregnant groups. However, the iron levels were lower in pregnant rats than those in the control. The liver and spleen iron contents increased significantly in the excess Fe group. An increase in liver ferritin levels with increasing iron intake was observed. Protein carbonyl content, as a marker of oxidative stress, increased significantly in liver with increasing iron intake but not malondialdehyde. Glutathione peroxidase activity in the liver of pregnant rats fed excess iron decreased significantly. Bcl-2 protein expression in the liver declined remarkably with increasing maternal iron intake in pregnant rats. Taken together, iron overload during pregnancy had little effect on hematology. However, the deposits of iron in the liver and the decline in antioxidant enzyme activity implied increased oxidative stress in tissues of the excess Fe group. These results suggest that excess iron intake during pregnancy increases oxidative stress in maternal tissues and may also affect fetal tissues.

Keywords: iron overload, pregnancy, oxidative stress, antioxidant enzyme

Figures and Tables

Fig. 1

The body weight and food intakes of non-pregnant and pregnant rats. A) The growth chart during experimental period. B) Food intakes during experimental period. Con-N: Non-pregnant Control fed normal Fe diet, Con-H: Non-pregnant Control fed high Fe diet, Con-E: Non-pregnant Control fed excess Fe diet, Pre-N: Pregnant rats fed normal Fe diet, Pre-H: Pregnant rats fed high Fe diet, Pre-E: Pregnant rats fed excess Fe diet. Values are mean ± SE of 6 rats per group. Bars with different letters are significantly different at p < 0.05 by Duncan's multiple range test.

Fig. 2

Protein levels of ferritin in liver of non-pregnant and pregnant rats. A) Western blots show the protein expression levels of ferritin in liver of non-pregnant (Control) and pregnant rats at three iron intake levels (N: normal, 35 ppm, H: high, 350 ppm, E: excess, 1,050 ppm). B) Bar graph represent the relative density of ferritin protein level in liver. ^*: means a significant difference from Con-N at p < 0.05.

Fig. 3

Protein levels of Bax, Bcl-2 and Caspase-3 of liver of non-pregnant and pregnant rats. A) Western blots show the protein expression levels of Bax, Bcl-2, Caspase-3 as a marker of cell apoptosis. Results represented that Bcl-2 protein level of pregnant rats fed exess iron decreased significantly compared with rats fed normal iron. B) Bar graphs represent the relative density of bax, bcl-2 and caspase-3 protein level in liver respectively.

^*: means a significant difference from Con-N at p < 0.05.

Table 1

Composition of experimental diets (g/kg diet)

1) AIN-93G purified diet 2) NFe: normal iron (35 mg/kg diet), HFe: high iron (350 mg/kg diet), EFe: excess iron (1,050 mg/kg diet) 3) AIN-93G mineral mixture 4) AIN-93 vitamin mixture 5) Fe pre-mixture: 101,500 mg Fe/kg

Table 2

Tissue weights of non-pregnant and pregnant rats

1) Values are Mean ± SE of 6 rats per group 2) a, b values with different superscript within a column are significantly different at p < 0.05 by Duncan's multiple range test 3) NS : not significantly different among groups

^*: p < 0.05, ^**: p < 0.01 by two-way ANOVA test

Table 3

Litter size, total fetus weight and total placenta weight of pregnant rats

1) Values are Mean ± SE of 7 rats per group 2) NS : not significantly different among groups

Table 4

Hemoglobin, hematocrit and serum iron concentration of non-pregnant and pregnant rats

1) Values are Mean ± SE of 7 rats per group 2) a, b, c values with different superscript within a column are significantly different at p < 0.05 by Duncan's multiple range test 3) NS: not significantly different among groups

^**: p < 0.01 by two-way ANOVA test

Table 5

Iron contents in liver, brain and spleen of non-pregnant and pregnant rats

1) Values are Mean ± SE of 6-7 rats per group 2) a, b values with different superscript within a column are significantly different at p < 0.05 by Duncan's multiple range test 3) NS: not significantly different among groups

^*: p < 0.05, ^**: p < 0.01 by two-way ANOVA test

Table 6

The contents of MDA and DNP in liver homogenates of non-pregnant and pregnant rats

^*: p < 0.05, ^**: p < 0.01 by two-way ANOVA test

Table 7

The activities of antioxidant enzymes in liver of non-pregnant and pregnant rats

^**: p < 0.01 by two-way ANOVA test

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