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HANDBOOK OF PHYSIOLOGY 



CIRCULATION 



nor acute splenectomy in the dog seems to influence 

 tlie disappearance rate. In our laboratory, 41 intact 

 barbitalized dogs had an average P'^ disappearance 

 of 5.25 per cent per hour, while 31 acutely splenecto- 

 mized dogs under the same anesthetic had an average 

 rate of 5.88 per cent (Lawson, unpublished data). 

 The near identity of disappearance rates in different 

 species and under different experimental conditions 

 is reassuring, in view of the fact that the turnover of 

 inorganic phosphorus is probably influenced by 

 metabolic processes (68). 



There appears to be no excessive loss of this label 

 during the mixing period, since its distribution volume 

 is the same as that of cells firmly tagged with Fe^^ 

 or Fe'' (22, 167), or with Cr^' (160). That its distribu- 

 tion space is the same as that of transfused unlabeled 

 cells has been shown by using the procedure described 

 in the introduction for equation 2 (see fig. 2). 



Radiochromium 



Cr*' was found by Sterling & Gray (87, 88) in 

 1950 to be rapidly attached to red cells in drawn 

 blood if it was added to blood in the form of the 

 hexavalent anion. As much as 90 per cent of added 

 chromium may become bound by erythrocytes in a 

 half-hour at room temperature (224). Most of the 

 Cr^' is bound to the globin moiety of hemoglobin 

 (88), and the binding appears to be quite stable 

 in vitro. If unlabeled red cells are incubated with 

 hemolyzed Cr"'-labeled cells, they take up none of the 

 label (60). When Cr^' is added to blood in the form 

 of the trivalent cation, very little enters the cells 

 but it combines with the plasma proteins. These 

 chromium-protein complexes also appear to be 

 quite stable in vitro, no transchromation being 

 demonstrable when labeled and unlabeled proteins 

 are allowed to stand together for periods of several 

 days (88). 



There is less certainty about the persistence of 

 Cr^'-labeled cells in the circulation. The labeling 

 slightly increases their mechanical fragility (164). 

 This may be partially responsible for the reduced 

 life span of Cr''''-labeled cells as shown by serological 

 techniques (60, 81, 164). Damage to the cells, as 

 suggested by such studies, is due to chromation 

 per se, and not to mishandling while the cells are 

 being treated, since identical decay cur\es for Cr^' 

 are obtained for cells prepared in \itro and injected 

 into the circvdation, and for cells chromated in vivo 

 by injecting Na2Cr*'04 into the subject (229). Slow 

 elution of Cr^' at the rate of about i per cent per 

 day can be demonstrated by suspending chromated 

 cells in saline, and dialyzing (164). 



Despite uncertainty about the life span of chro- 

 mated cells, there is no evidence of excessive destruc- 

 tion during the mixing period. The distribution 

 space calculated for them is the same as that of re- 

 labeled cells (160). E.xcept for the initial mixing 

 period, the rate of Cr^^ disappearance from blood is 

 exponential throughout, including the first day, 

 unless very high concentrations of chromium are 

 employed (125). 



Other Radioactive Labels 



Insufficient data have been presented on otlier 

 radioactive labels to permit their evaluation. Cells 

 labeled in vitro with K*' have been reported to 

 have the same virtual distribution space as those 

 labeled with P^' (243). Thorium B has been proposed 

 as a suitable cell label for blood volume studies 

 (ill, 112), and it has been suggested that firm P^- 

 labeling be accomplished by administering to donors 

 the drug diisopropylfluorophosphonate with the 

 phosphonate group containing the radioisotope 

 (41). 



REFERENCES 



1. .Abderhalden, E., and J. ScHMiD. Bestimniung der 

 Blutmenge mit Hilfe der "Optischen Mcthode." Ztsclir. 

 Physiol. Chem. 66: 120, 1910. 



2. Abell, R. G. The permeability of blood capillary sprouts 

 and newly formed blood capillaries as compared to that 

 of older blood capillaries. Am. J. Physiol. 147: 237, 1946. 



3. Adolph, E. F., M. J. Gerb.'\si, and M. J. Lepore. The 

 rate of entrance of fluid into the blood in hemorrhage. 

 Am. J. Physiol. 104: 199, 1945. 



4. Allen, T. H., and M. I. Gregersen. Measurement of 

 plasma volume in the dog with high concentrations of 

 T-1844. .-Im. J. Physiol. 172: 377, 1953. 



5. ,\llen, T. H., M. OciioA, R. F. Roth, and M. I. 

 Gregersen. Spectral absorption of T-1844 '" plasma of 

 various species and recovery of the dye by extraction. 

 Am. J. Physiol. 175: 243, 1 953. 



6. .Allen, T. H., and P. D. Orohov.\ts. Combination of 

 toluidine dye isomers with plasma albumin. .4m. J. 

 Physiol. 161 : 473, 1950. 



7. .\llen, T. H., C. Pallavicini, and M. I. Gregersen. 

 .Simultaneous measurement of plasma volume with 

 hemoglobin and with T-1824. Am. J. Physiol. 175: 236, 



■953- 



8. .Allen, T. A., and \V. S. Root. Partition of carbon 



