Vitellogenin induction in quail is diminished by a marginal Zn diet

Previous studies from the authors' lab have suggested that the rate of estrogen-directed gene expression accompanying the onset of labor is reduced in pregnant rats fed a diet low in zinc from day 10 of gestation. This effect appears to be distinct from a general effect on the synthesis of cellular protein. The estrogen receptor (ER) is a member of a superfamily of ligand-activated transcriptional regulators which contain the Zn finger motif. Timely acquisition of Zn by ER may be a rate limiting step when the Zn supply is marginal. The authors have tested this phenomenon further in the quail. Five week old sexually mature male Japanese quail were fed a semi-purified diet containing either 147 or 1-2 ppm of zinc for a three week period. Dietary Zn content had no effect on feed consumption or weight gain but plasma Zn declined from 2.6 {plus minus} 0.2 {mu}g/ml to 1.6 {plus minus} 0.2 {mu}g/ml and liver Zn fell from 133 {plus minus} 7 {mu}g/g to 79 {plus minus} 5 {mu}g/g. Estrogen challenge in controls was followed by the appearance of 0.66 {plus minus} 0.04 mg protein bound phosphorus (PBP) in the plasma which represented liver synthesis of the egg-yolk proteinmore » vitellogenin. Low Zn-fed birds produced only 64% as much PBP.« less