77 

 of equal levels of Zn and Cu . Liver levels reported in the 

 same study (42 ± 3 |ig MT/g) were similar to those of our 

 supplementation phase but higher than those of depleted rats. 

 Furthermore, dietary Cu level was reported (Blalock et al . , 

 1988) not to affect kidney MT concentration. The present 

 study, the lowest available Cu source showed the lowest MT 

 concentration, suggesting that Cu does influence MT expression 

 when the available dietary Cu is very low. Following the week 

 of depletion all MT levels stabilized and no differences were 

 observed for different treatments. These results indicate 

 that, at adequate supplemental levels, organic sources of Zn 

 and Cu are metabolized similarly in most aspects as the best 

 inorganic sources (CuS0 4 and ZnS0 4 ) . 



Implications 



When supplementing adequate dietary levels of Zn and Cu 

 (30 and 6 mg/kg, respectively), CuO is less available than 

 CuLys and CuS0 4 , however under the conditions of this 

 experiment, organic (ZnMet and ZnLys) and inorganic (ZnSOJ 

 sources of Zn were similar in bioavailability. 



Summary and Conclusions 



A study was conducted to compare bioavailability, 

 interactions and retention of different sources of Zn and Cu 

 fed to rats. Sixty-three male CD rats were fed individually 

 a purified diet and deionized water ad libitum. The nine 



