Studies with nonradioisotopic sodium chromate. I. Development of a technique for measuring red cell volume

Abstract

A nonradioisotopic metod for measuring red cell volume that involves the use of 52Cr-sodium chromate as the red cell label and of graphite furnace atomic absorption analysis of chromium is described. The technique allows the labelling of 20 mL of packed red cells with 40 to 50 .mu.g of sodium chromate (Na2CrO4) in 30 minutes at 22.degree.C with 94 .+-. 6 percent uptake. Approximately 40 .mu.g of Na2CrO4 was injected for in vivo studies. This results in posttransfusion in vivo red cell chromium levels after sample processing in the range of 1 to 7 .mu.g per L, which could be quantitated accurately (coefficient of variation = 4.7%) by Zeeman electrothermal atomic absorption spectrophotometry. The labeling concentration of chromium did not cause increased hemolysis, and the labeled cells exhibited an osmotic fragility curve similar to that of unlabeled, fresh ACD red cells. Red cell glutathione peroxidase was unaffected by labeling, although glutathione reductase was reduced by approximately 13 percent (p < 0.05). The 52Cr red cell volume-measuring method was evaluated by concurrent in vivo studies with the standard 51Cr and 125I-albumin methods for the procedure. Simultaneous measurement of red cell volumes in seven volunteers by the 51Cr, 52Cr, and 125I-albumin techniques correlated highly with each other (r > 0.76), with mean values of 2294 .+-. 199, 2191 .+-. 180, and 2243 .+-. 291 mL, respectively. The standard deviations of the differences were small: 134 mL for 52Cr versus 183 mL for 52Cr versus 125I. These results indicate that the nonradioisotopic technique gives reliable and accurate red cell volume estimates that are similar to those obtained by the standard methods.