Laboratory assessment of early dietary, subclinical zinc deficiency: a model study on weaning rats

Male weaning rats were pair-fed a low-zinc diet or a control diet. After 10 d, the animals fed the low-zinc diet showed physiologic signs of deficiency; however, they showed no clinical symptoms. Their estimated whole body zinc was 25 mumol versus 39 mumol for the controls. The 65Zn absorption increased 2-fold and the tissue distribution altered: muscle and erythrocytes contained more, small intestine and liver less activity at 0.5 h postdose. In vitro, the erythrocyte 65Zn uptake rate increased also. The 65Zn uptake experiments required small quantities of erythrocytes. The difference observed between the deficient and control cells was significant and showed little overlap. The increase of the 65Zn uptake from a medium was not affected when the animals underwent endotoxin exposure 24 h before, as was reported to occur in whole blood 65Zn uptake. Therefore, we suggest the in vitro erythrocyte 65Zn uptake, performed in a standardized, near physiologic medium, to detect early, subclinical zinc deficiency.