Chromium (III) metabolism by the kidney.

The kidney is the principal route of excretion of the essential trace element chromium. Previous studies suggest that five to 40 percent of plasma chromium (III) is ultrafilterable and that 60 to 95 percent of filtered chromium is reabsorbed in the renal tubule. However, less than five percent of a stable Cr (III)-EDTA chelate is reabsorbed; therefore, this complex has been used to measure glomerular filtration. An increased fractional excretion of chromium may result from a glucose challenge or from a volume diuresis. These mechanisms have been postulated to cause an increased urinary excretion of chromium in patients with diabetes mellitus. Investigations of chromium metabolism and excretion must be interpreted with caution because chromium analysis is known to be subject to many sources of error and chromium (III) salts may not be physiologically equivalent to biological chromium complexes. Analytical refinements should permit further delineation of normal chromium homeostatic mechanisms and allow better identification of abnormalities in chromium metabolism.