Radioactive sodium chromate for the study of survival of red blood cells. I. The effect of radioactive sodium chromate on red cells.

Abstract

HE usefulness of radioactive sodium chromate (NaCr”‘0,) as a tracer substance for the measurement of blood volume was reported by Gray and Sterling in 1950.‘9 2 Their data suggested that the radiochromate method could not be employed to study red-cell survival time since the CI+ disappeared from the circulation more rapidly than could be explained on the basis of the known rate of destruction of red cells as demonstrated by the Ashby method,3 or by isotopic technique using N1”, Fes9, or C14.(4-F) Since the curve for the disappearance of Cr”l from the blood is approximately linear with respect to time, it occurred to us that the chromium-labeled red cells could be used to make relative estimates of the survival of erythrocytes under clinical conditions. Because of the simplicity and the versatility of the radiochromium technique, it seemed desirable to explore this possibility even though it was evident that absolute survival time could not be determined directly. In this paper we report preliminary studies that were undertaken to investigate : (1) the nature of the combination of NaCPO, with the red cell; (2) the effect of the chromat,e on the cell; (3) the rate of elution of Cr 51 I’rom the cells ; and (4) the normal appa.rent survival curves. METHODS AND RESULTS Whole blood, either heparinized or in ACD solution, was diluted with one-half volume of physiologic solution of sodium chloride. To this was added radioactive sodium chromate* in sufficient amount to give approximately 200 gc per 100 ml. of blood. The mixture was allowed to stand at room temperature for one hour with frequent agitation. The blood was then centrifuged in the rold for fifteen minutes at 2,000 r.p.m. and the supernatant removed. The red cells were washed three times in this manner, and then resuspended in cold salt solution. An aliquot was taken for the preparation of a-standard, and the remainder was either reinjected or used for in vitro experiments. The effect of the anticoagulant used is shown in Table I. It is evident that somewhat better labeling is obtained using ACD, although the difference is not sufficiently great, to interfere with our studies. The radiation measurements were made using either the Texas-type well counter, or a well-type crystal counter. With