Copper and zinc distribution in the liver and oviduct of estrogen- and testosterone-treated hens ( Gallus domesticus)

Abstract

Sexually immature (12 weeks-of-age) and mature (22 weeks-of-age) hens were randomly assigned to one of three hormone treatments (control, 17β-estradiol, or testosterone) in a 2×3 factorial arrangement to determine the effects of exogenous estrogen and testosterone on hepatic intracellular distribution of copper and zinc. Hormone treatments were administered in subcutaneous polydimethylsiloxane implants for five weeks. Plasma copper concentrations were higher (P<.05) in mature than in immature hens, but were not influenced by hormone treatment. Maturity had no effect on hepatic copper concentrations, but hepatic zinc was higher (P<.05) in mature than in immature hens. Copper and zinc distribution within the subcellular fractions of the liver was altered by both sexual maturity and steroid treatment. Immature hens had more (P<.05) copper in the large granule (mitochondria, lysosomes) and microsome fractions and less (P<.05) zinc in the debri (nuclei) and microsome fractions than mature hens. Microsome copper was two-fold greater in estrogen-treated, immature hens than in any other treatment. Gel filtration chromatography of liver cytosol revealed that more zinc was associated with binding proteins of >150,000 and 10,000 daltons in mature hens, but little difference in protein copper content was observed between ages. Whole oviduct copper concentrations in mature control hens were greater than in any other treatment. These results suggest that at sexual maturity in the hen, alterations in copper and zinc distribution and metabolism occur which differ somewhat from the age-related changes observed in mammals. Such shifts may reflect an increased requirement for copper or zinc in egg formation and reproduction.