75 

 Since tissue Zn concentrations were not affected by Zn 

 source, this may suggest equal metabolism of all Zn sources in 

 those tissues at this level of supplementation. Copper, 

 however, may be involved in bone Zn deposition since CuO 

 treated rats, which was less available, had lower bone Zn than 

 CuLys treated rats. Most tissue Zn concentrations decreased 

 during depletion, but bone showed no change. Kidney Zn 

 concentrations of CuO supplemented rats were inexplicably 

 higher than those of CuS0 4 . Zinc retention based on tissue 

 data for the different treatments was not affected. 



Mean tissue Cu concentrations reflected the same trends 

 as plasma concentrations indicating that CuO was less 

 bioavailable than CuLys or CuS0 4 . Furthermore, CuS0 4 

 supplemented rats had the highest muscle Cu concentrations 

 which suggests that Cu from this source is taken up by muscle 

 cells more readily. The only tissue to retain the same 

 proportions of Cu following depletion to those before the 

 beginning of depletion was the liver, as liver Cu 

 concentrations of CuO supplemented rats were lower than other 

 treatments. Kidney and muscle Cu concentrations, however, 

 stabilized and there was no difference for the different 

 sources, suggesting a lower retention for CuLys and CuS0 4 . 

 Copper retention in those tissues, represented by the lack of 

 difference among sources, might also be influenced because Cu 

 levels were marginal for rat tissues treated with CuO which 

 had low plasma Cu concentrations. 



