Dialysis Studies of Liver Zinc in Zinc-deficient and Control Rats

Abstract

Experiments were designed to study possible effects of zinc deficiency on zinc binding by rat liver. Either 3 hours after intravenous ⁶⁵Zn injection or after 10 days of feeding ⁶⁵Zn-containing diets, low zinc (-Zn) and zinc-supplemented (+Zn) rats were killed and liver homogenates dialyzed against 8 successive volumes of buffered 10^-3M EDTA, CDTA, histidine, cysteine, glycine, or buffer alone. Based on the dialysis results, liver zinc was delineated into 4 pools. When ⁶⁵Zn was fed for 10 days to label zinc pools uniformly, dietary zinc deficiency had no significant effect on the amount of ⁶⁵Zn removed by any of the dialyzing agents, which suggests that the binding pattern of liver zinc, like that of total zinc concentration, is not altered in zinc deficiency. When ⁶⁵Zn was injected intravenously, the percentage of liver ⁶⁵Zn removable at 3 hours postinjection by EDTA, but not by histidine, was significantly smaller in -Zn than in +Zn rats. This suggests that the rate of incorporation of zinc into certain liver pools is altered in zinc deficiency. Explanations for this effect were suggested, based on the difference in growth rate between the +Zn and -Zn rats and on the possible increase in the turnover rate of a firmly bound zinc pool in zinc deficiency.