Equilibrium distribution of radioxenon in tissue: xenon-hemoglobin association curve

In vitro and in vivo studies were made of the equilibrium distribution of radioxenon in various organs and tissues of the dog and the xenon uptake compared with a water standard. Tissue-blood partition coefficients were calculated. The radioxenon-hemoglobin association curve was determined for dog and human hemoglobin and methemoglobin. The uptake of radioxenon by blood, due in particular to xenon-hemoglobin affinity, was appreciably greater than uptake either by water or by most other body tissues. Fat and brain were notable exceptions. Consequently, tissue-blood partition coefficients were about eight for fat, one for brain, and significantly less than one for other tissues studied. Acceptable accuracy for blood flow determinations with a radioxenon inert gas diffusion method would seem to depend on the use of a partition coefficient correction in turn corrected at least for the existing hemoglobin concentration. The uptake of xenon by hemoglobin had the characteristics of a solubility or a quasi-solubility phenomenon. The problem of the nature of the interaction is apparently not resolved. Submitted on June 19, 1961