Abstract
Summary
The ingestion by normal adults of a standard oral glucose load (75 g) resulted in a significant decrease of the fasting rate of urinary excretion of the trace metal chromium. This effect was not accompanied by any significant parallel change in GFR. Copper excretion rate was not significantly changed by the glucose load. In contrast with the effect of a glucose load, diuresis, induced by a water load, increased the excretion rate of both chromium and copper by more than 100%. The increases in metal excretion with diuresis were not attributable to increased GFR.
Observations on the renal excretion of chromium and copper in the dog showed that tubular reabsorption of chromium and copper was greater than 98% in normal fasting conditions. In dogs receiving intravenous infusions of hypotonic saline and of vasopressin, a marked correlation was obtained between urine flow rate, the chromium and copper excretion rates, and also the fraction of the filtered loads of the metals excreted. However, tubular reabsorption of chromium and copper was greater than 97% even at maximal urine flow rates. These observations suggest that the kidney of both man and dog may possess an active tubular reabsorptive capacity for chromium and copper.
We are grateful to Professor J. Maxwell Little for helpful discussions and suggestions, and we thank W. L. Secrest for expert technical assistance. These studies were supported in part by NIH Grant No. RR-5404.
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