COPPER ABSORPTION, ENDOGENOUS EXCRETION, AND DISTRIBUTION IN SPRAGUE-DAWLEY AND LEAN (FA FA) ZUCKER RATS/

We previously observed a rapid reduction in plasma ceruloplasmin activ ity in lean Zucker (Fa/Fa) rats fed a marginal copper (Cu)-deficient d iet compared to similarly fed obese Zucker (fa/fa) and lean Sprague-Da wley rats. In an effort to understand the mechanisms underlying this r esponse, we utilized the isotope dilution method to investigate the ab sorption and excretion of Cu in lean Zucker rats fed control and margi nal Cu diets, Sprague-Dawley (SD) and homozygous lean Zucker rats were fed either a Cu-adequate (Cent; 7.5 mu g Cu/g diet) or a low Cu (Low; 1.1 mu g Cu/g diet) casein-based diet for 23 d. Two weeks following i nitiation of the dietary treatment, each rat was injected intramuscula rly (im) with 11.2 mu Ci of Cu-67. Urine and feces were collected dail y. On the 9th d following isotope injection, rats were killed and tiss ues collected. Significant dietary effects were observed in the relati ve absorption and endogenous fecal excretion of Cu-67. The tissue dist ributions of nonisotopic Cu and Cu-67 activity were also different bet ween dietary treatments. Tissues from rats fed the low-Cu diet typical ly had high concentrations of Cu-67 and low concentrations of nonisoto pic Cu compared to controls. An increase in relative Cu-67 absorption was evident for rats fed the low-Cu diet (57.2 and 39.3%, for SD Low, Zucker Low respectively, and 17.9, and 28.5% SD Cent and Zucker Cent, respectively). Rats fed the low-Cu diet also had reductions in endogen ous fecal excretion of Cu-67 compared to their respective controls. Al though strain effects were not evident for either percent Cu absorptio n or endogenous fecal Cu excretion, the relative adaptive changes appe ared more marked for the Sprague-Dawley rats compared to the lean Zuck er rats.