394 



4. ALLOXAN 



surprising that the tissue levels remain so high after 30 min. He used 

 the o-phenylenediamine reaction to determine alloxan and it may be that 

 some of the metabolic products contribute. It is often stated that alloxan 

 is destroyed mainly in the liver but I know of no evidence for this; indeed, 

 the results of Fister et al. (1957) indicate that various tissues are able to 

 metabolize alloxan. 



The use of radioactively labeled alloxan has provided further informa- 

 tion on the distribution and fate of alloxan. Alloxan-l,3-Ni^ injected in 



Fig. 4-4. Tissue levels of alloxan in rats following 



intravenous injection of 200 mg/kg. The data given 



are irregular and the curves are very approximate. 



(Data from Siliprandi, 1948.) 



diabetogenic doses in rats and rabbits was recovered mainly in the nonpro- 

 tein fractions of tissues, after 1 hr highest concentration occurring in the 

 kidney (Lee and Stetten, 1952). The pancreatic level is always rather low. 

 Only two thirds of the injected isotope is excreted in the urine within 3 

 days, so significant amounts of the alloxan metabolites must be incorporated 

 into the tissues. Injection of alloxan-5-C^* or alloxan-2-C^^ gives a much 

 higher recovery (90-95%) in the urine during the first day (Janes and 

 Winnick, 1952). Almost no C^^Og appears, indicating that alloxan is not 

 catabolized. About 80% of the urinary activity is probably alloxanate. 



