The effect of depot parenteral zinc on copper metabolism in the rat.

The effect of depot parenteral injections of zinc (110 mg Zn/kg body weight) on copper metabolism in young, male rats was investigated. Individually caged rats, fed known amounts of stock diet and deionized-distilled water, were injected s.c. weekly for the first 4 weeks and biweekly for the next 17 weeks with zinc in sesame oil or the oil vehicle only. No significant differences in body weight, hemoglobin, hematocrit and fecal copper excretions were observed between treatments. However, 2 weeks after the initial injections, urinary copper excretion was elevated in the zinc-injected animals and remained elevated throughout the rest of the study. Plasma copper concentrations were significantly higher in the zinc-injected animals from week 2 to 8 of the study, and plasma zinc concentrations of these injected animals were elevated (P less than 0.05) from week 2 and throughout the remainder of the study. Zinc concentrations were significantly higher in the liver, heart, kidney and spleen (P less than 0.05) and copper concentrations were lower in the liver (P less than 0.07), kidney and spleen (P less than 0.05) of zinc-injected animals compared to the vehicle-treated control animals. The data indicate that when zinc is administered by a non-gastrointestinal route, the fecal excretion of copper, the major route of copper excretion, is not altered. Thus, a negative copper balance is not initiated by high levels of zinc administered by the depot technique, in contrast to the negative copper balance stimulated by the gastrointestinal administration of zinc.