518 XI. HEMOGLOBIN CATABOLISM, I 



Dehydroascorbic acid can be reduced by reduced glutathione (320,1710, 

 2If85). Schultze, Stotz, and co-workers {:2I^82,2I^85,2678,2679) have shown 

 that the oxygen uptake of Hver and kidney tissue is not increased by the 

 ascorbic acid - ghitathione system. This, however, proves only that this 

 system does not play a major part in normal tissue respiration. In erythro- 

 cytes in which the respiration is much smaller, the system may be of relatively 

 greater importance. Davis, indeed, has assumed that ascorbic acid is involved 

 in red cell respiration on the basis of experiments on cobalt polycythemia 

 {539, cf. Chapter XIII), but definite evidence is not yet available. 



The reduction of hem/globin in solution by ascorbic acid has been studied 

 by Lemberg and co-workers {1710), Vestling {2873), Gibson {993), and Kiese 

 {1526). Kiese found the rate of reduction proportional to the hemiglobin 

 concentration, but reaching a limiting value with increasing ascorbic acid 

 concentration; from this he concluded that a complex is formed and that the 

 reduction of the hem/globin iron in this complex is the limiting velocity. 



4. HEMIGLOBINEMIA (METHEMOGLOBINEMIA) 

 4.1. Hemiglobin as Normal Component of the Erythrocyte 



In the previous section it has been shown that the erythrocyte 

 is well supplied with reducing systems, and it has been suggested 

 that they are concerned in part with the reduction of hemiglobin 

 within the cell. While this view is generally accepted, little evidence 

 is available concerning the mode of formation of the hemiglobin under 

 normal conditions. 



The hemiglobin concentration in normal blood is still a matter of 

 dispute. Claims that 15-20% of the total hemoglobin can be in the 

 form of hemzglobin without being spectroscopically detectable 

 (4^8,1254,1388) are certainly incorrect (508). Drabkin and Schmidt 

 (632) found that hemiglobin concentrations of above 1% can be 

 readily detected by spectrophotometry and that normal human 

 blood must contain a smaller concentration (cf. also Chapter X, 

 Section 5.3.). Jope (1427) found 3% hemiglobin readily detectable 

 in the Ilartridge reversion spectroscope. Heubner (1254) gives the 

 following average values for the hemiglobin content of normal blood 

 (in per cent of total hemoglobin): man, 1.7 (1.1-2.4); dog, 0.6; 

 rabbit, 1.5 (0.9-1.8); cat, 1.9; horse blood may contain more hemi- 

 globin. Lower values have been found by Paul and Kemp (2122): 

 man, 0.6 (0-2.5).* 



From the figure of Ramsey and Warren {2201) for the respiration 



* Cf. also Kiese {15-^Oa), Heubner and co-workers {l'26'2a). Van Slyke and co-workers 



{257 >,a). 



