Effects of zinc and/or iron deficiency on rectal temperature in rats

O'Dell et al. reported that rectal temperature was decreased by zinc deficiency in rats. However, it is not known whether a combined deficiency of zinc and iron affects rectal temperature. Forty 4-wk-old male Sprague-Dawley rats were assigned into four dietary treatment groups of 10 rats each for the 4-wk study: zinc-deficient group (4.5 mg Zn and 35 mg Fe/kg diet; -Zn), iron-deficient group (30 mg Zn/kg diet, no supplemental iron; -Fe), zinc/iron-deficient group (4.5 mg Zn/kg diet, no supplemental iron; -Zn-Fe), and control group (AIN-93G; Cont). At d 24-27, the rectal temperature was determined. The rectal temperature of the -Zn group was significantly lower than the Cont group. The rectal temperature of the -Zn-Fe group was similar to that of the Cont group, although thyroid-stimulating hormone and total thyroxin concentrations were the lowest in the -Zn-Fe group among all groups. The pattern of the plasma nitrate/nitrite concentrations across groups was similar to rectal temperature. Although observation of the rectal temperature is not conclusive, the balance between zinc and iron intake seems to determine the body temperature set point. These results suggest that the thermogenic effect of thyroid hormones is not thought to influence the paradoxical maintenance of rectal temperature in combined deficiency of zinc and iron.