Decline in serum zinc level throughout adult life in the laboratory mouse.

The objective of the study was to test the hypothesis that age and serum zinc level exhibit a negative correlation in the adult mouse. Fifty-seven male CBA/J mice were fed ad libitum, for 14 days, a semisynthetic diet containing 8 micrograms zinc per gram, a level that meets but does not exceed the weanling growth requirement for this nutrient under our conditions. At the end of the feeding trial the mice ranged in age from 7 to 87 weeks. Regression analysis indicated a linear decrease in serum zinc level with advancing age throughout adult life (Y = 0.70 - 0.0029 X, where Y is zinc level in micrograms/ml and X is age in weeks). The relationship was not changed significantly when adjusted for the effects of serum protein concentration, initial live weight, or 14-day weight gain and feed intake. The results suggest that the dietary zinc requirement increases progressively as an age-related phenomenon.