Plasma whole blood and urine zinc in the assessment of zinc deficiency in the rat.

Serial measurements of plasma, whole blood, and urine zinc have been made in young adult rats fed zinc deficient and zinc supplemented diets for a total period of 65 days. After commencing a zinc deficient diet plasma zinc fell within 48 hours to 25% of control values and remained at this level throughout the period of study. A substantial diurnal variation was observed in plasma zinc, and the level was significantly lower in the fasting state. Whole blood zinc was unaffected by fasting, showed no diurnal variation, and remained at control values even after 65 days of zinc deficient diet. Urine zinc fell to very low values, 10 days after commencing a zinc deficient diet, but after 30 days rose to control values. Under controlled conditions plasma zinc can be used as an indication of zinc deficiency. Whole blood zinc is of no value in the detection of zinc deficiency. Urine zinc concentration varies with time following a zinc deficient diet.