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Copper Absorption and Copper Balance during Consecutive Periods for Rats Fed Varying Levels of Dietary Copper^1,2,

U.S. Department of Agriculture, Agricultural Research Service, Grand Forks Human Nutrition Research Center, Grand Forks, ND 58202

Copper (Cu) balance and absorption were studied to determine the extent to which absorption is dependent on dietary Cu. Over 12 consecutive 5-d metabolic periods, Cu balance was determined for four groups of young growing rats (n = 8) fed modified AIN-76 diets having different levels of added Cu (2.5, 5.0, 10 or 20 µg/g). Among groups, mean body weights did not differ over time (P > 0.05). There were no significant differences among groups for liver, heart or plasma Cu. Rats in all groups were in positive Cu balance throughout the study. After consuming the experimental diets for 10 d, rats eating 10 or 20 µg Cu/g diet showed a more positive Cu balance than did rats in the other groups. This trend continued until d 60. For rats eating 20 µg Cu/g diet, balance varied significantly over time. Three test meals labeled with stable ⁶⁵Cu were fed at d 10, 40 and 50, respectively. Apparent Cu absorption, as determined by fecal monitoring of ⁶⁵Cu, did not change appreciably over time for rats eating 2.5 or 5.0 µg Cu/g diet. A test meal labeled with radioactive ⁶⁷Cu was fed at d 40. For rats eating 2.5 µg Cu/g diet, apparent absorption was higher (31%) than that for all other groups (5.0, 23%; 10, 19%; 20, 16%; P < 0.05). Absorption values determined by whole-body retention of ⁶⁷Cu were similar to those determined by fecal monitoring of ⁶⁵Cu.

KEY WORDS: • copper absorption • copper balance • stable isotopes • radioisotopes • liver copper • heart copper • plasma copper

¹ A summary of the results of this study was presented at the 69th annual meeting of the Federation of American Soceities for Experimental Biology, Anaheim, CA, April 1985. Stuart, M. A. & Johnson, P. E. (1985) Copper absorption and measurement of copper balance during consecutive periods for rats fed varying levels of dietary copper. Fed. Proc. 44, 54 (abs. 757).

² Mention of a trademark or proprietary product does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture, and does not imply its approval to the exclusion of other products that may also be suitable.

³ Present Address: University of Kentucky Medical Center, Department of Gastroenterology, Lexington, KY 40536.

⁴ To whom reprint requests should be sent.

Manuscript received 19 July 1985. Revision accepted 5 February 1986.