Binding of [51Cr]ethylenediaminetetraacetate to proteins of human plasma

Binding of [51Cr]EDTA to human plasma proteins was investigated using chemical and chromatographic techniques of separation of the proteins and protein fractions. Total plasma proteins isolated with ethanol retained 12.95 +/- 0.46% of the initial plasma activity. Proteins separated by other precipitants retained about 16% of the initial radioactivity. Globulins exhibited the highest binding capacity for [51Cr]EDTA and retained about 11.7% of the initial plasma activity following chromatographic separation. This value represents about 70% of the radioactivity bound by the total proteins of the plasma. gamma-Globulins contributed most of the binding attributed to the globulins and retained about 8.7% of the initial [51Cr]EDTA activity. The repeatedly reported underestimation of the renal glomerular filtration rate when estimated as the clearance of [51Cr]EDTA could be adequately accounted for by the extent of binding of this marker to the plasma proteins.