SIZE OF THE ZINC POOLS THAT EXCHANGE RAPIDLY WITH PLASMA ZINC IN HUMANS - ALTERNATIVE TECHNIQUES FOR MEASURING AND RELATION TO DIETARY ZINCINTAKE

A relatively simple technique was used to estimate the size of the com bined pools of zinc with which plasma zinc exchanges within 2 d (EZP). EZP size was determined from the amount of isotope introduced into th e plasma and the coefficient of the simple exponential decay function fitting enrichment data between d 3 and 9 after isotope administration . Using data from 11 healthy adults, comparisons were made of EZP size estimations using oral and intravenous isotopes (r = 0.93 using urine ) and urine and plasma enrichment (r = 0.85 for intravenous). EZP size estimations from urine and plasma enrichment following intravenous is otope administration were 2.35 +/- 0.84 and 2.83 +/- 0.86 mmol, respec tively (mean +/- SD, P < 0.01). EZP size correlated with habitual diet ary zinc intake (partial r = 0.74, P < 0.02). Cumulative declines in E ZP size in two healthy adults after 3 wk of consuming a moderately zin c-restricted diet followed by 1 wk of severe zinc restriction were 26 and 32%. These results indicated that EZP size is dependent on dietary intake. We conclude that this technique is adequate to demonstrate EZ P differences that are of nutritional and physiological interest. EZP size estimates can be obtained using orally or intravenously administe red isotope and using plasma or urine enrichment data.