BREAKDOWN OF MYOHEMOGLOBIN 543 



tion that the liver can transform sulfhemoglobin to biHrubin is, however, of 

 interest (c/. Chapter X). 



Observations of Briickmann and Zondek (362) indicate that occasionally 

 abnormal amounts of bile pigment hematins occur in organs. Extracts with 

 methanolic hydrochloric acid normally show a brown color due to hematin, 

 but in these instances they were green owing to the presence of biliverdin. 

 The green color of the chloroma tumor has been ascribed to the protopor- 

 phyrin which is found in it {cf. Chapter XIII), but this is not correct. Treat- 

 ment with carbon monoxide and dithionite produces an absorption band at 

 630 m/i {1706). This cannot be due to myeloperoxidase (Chapter IX, Sec- 

 tion 3.6.) since the chloroma tissue is known to contain little peroxidase {cf, 

 Thomas, 2798) and is probably the band of carboxycholeglobin.* 



7.5. Breakdown of Myohemoglobin 



It is still doubtful to what extent if at all the myohemoglobin of 

 the muscle is normally metabolized. The increased bilirubin excre- 

 tion after exercise, observed by McMaster and co-workers in the 

 bile fistula dog {1826), is due to increased hemolysis, not to greater 

 destruction of myohemoglobin (5^5). Whipple and co-workers 

 (354-8,3058) found increase of urobilinuria in the dog after intrave- 

 nous, intraperitoneal, or intramuscular injection of myohemoglobin 

 and a prompt conversion of it into bilirubin if given intravenously. 

 Myohemoglobin is transformed into myocholeglobin by coupled 

 oxidation with ascorbic acid, and is thus a potential source of bile 

 pigment. These experiments do not prove, however, that myohemo- 

 globin suffers destruction in the intact muscle cell. Whipple {30Jf7) 

 found a rapid decrease of myohemoglobin in the muscle after its 

 nerve supply was cut. Heilmeyer {1206) has suggested that the 

 urobilinuria in apoplexy, paralysis, and encephalitis may be due to 

 release and destruction of myohemoglobin, but Watson (2989, 

 p. 2499) suggests a temporary dysfunction of the liver as the expla- 

 nation. In pathological myohemoglobinuria, jaundice occurs (4-08), 

 but again the bilirubin is probably derived from myohemoglobin in 

 the circulating blood. In progressive muscular dystrophy and also 

 during the early stages of puerperal involution, Meldolesi and co- 

 workers (1898) found no increase of bile pigment excretion but an 

 increase of the fecal excretion of myobilin, the peptide of the dipyr- 

 rolic compound mesobilifuscin (cf. Chapter IV, Section 5.5.1.). This 

 pigment was also observed in small amounts in normal serum and 



* Humble {1367a) also identified the pigment with choleglobin, although he found 

 strong peroxidative activity of the tumor tissue. The ^sence of the Soret band sup- 

 ports the assumption that the pigment is choleglobin and not myeloperoxidase. 



