Search

To examine diurnal patterns of milk zinc concentrations, midfeed samples were obtained at approximately 6 a.m., 9 a.m., 12 noon, 3 p.m., 6 p.m., and 9 p.m. on a total of 29 days from 16 lactating women. Within-feed patterns were examined in 32 subjects with analysis of samples of fore-, mid-, and hindmilk from a total of 175 feeds. There were no significant differences between means for any of the diurnal intervals or between means for fore-, mid-, and hindmilk samples. These results indicate that milk zinc concentrations of random samples of human milk collected at any time of the day or of the feed can be accepted as representative for that day.

The effect of time between collection and separation of blood samples obtained from 9 subjects was examined with respect to plasma and serum zinc concentrations. There was a linear increase of 6% in zinc concentrations for the first 2 h that was similar for plasma and serum. Plasma zinc continued to increase linearly over the next 2 h, but increase in serum zinc concentrations was less for the second 2 h. It is concluded that differences between heparinized plasma and serum zinc concentration observed previously in this laboratory and elsewhere are attributable primarily to differences in time between collection and separation.

The metal-binding protein metallothionein was isolated from the livers of Wilson's disease patients and control subjects. The metals were removed from the native protein to produce the apoprotein, and copperthionein was prepared by equilibrium dialysis. Copperthionein from Wilson's disease patients had a copper-binding constant four times as great as that of the protein from control subjects. These results suggest that the alterations in copper homeostasis in Wilson's disease result from the synthesis of an abnormal metal-binding protein with an increased affinity for copper.