CIRCULATING RED-CELL VOLUME AND RED-CELL SURVIVAL CAN BE ACCURATELY DETERMINED IN SHEEP USING THE [C-14] CYANATE LABEL

The sheep commonly serves as an animal model for investigation of huma n fetal and newborn erythropoiesis and red blood cell kinetics. Measur ement of red cell volume (RCV) and survival (RCS) in sheep would be us eful for studying mechanisms of neonatal anemia. Unfortunately Cr-51, the standard method for RCV, is not suitable for RCS in sheep because Cr-51 leaves the red cell too rapidly. We developed and validated the permanent label [C-14]cyanate as a method for measuring both RCV and R CS in sheep. In 19 sheep, RCV was determined simultaneously using [C-1 4]cyanate and Cr-51. RCV determined by [C-14]cyanate agreed almost per fectly with RCV by Cr-51; correlation coefficient = 0.990. The line of regression had a slope of 0.94 and an intercept of 40; these paramete rs are not significantly different from a line of identity. In nine sh eep, RCS was determined using [C-14]cyanate. Survival after d 1 accura tely fit a model containing two components: 1) an early exponential lo ss likely related to damage caused by labeling and handling and 2) a l inear decrease that reflected normal survival of undamaged red cells. Mean potential life span (MPL) determined from the linear phase was 11 4 +/- 12 d (mean +/- 1 SD). These results agree with reported MPL valu es determined either by Fe-59 or differential hemolysis. Together, the se observations establish [C-14]cyanate-labeled red cells as a tool fo r measuring both RCV and RCS in sheep and enhance the value of the ovi ne model for investigating neonatal anemia.