144 III. OXIDATION AND METABOLISM 



the summer, while the average was only 1.9 mg. per day in the winter. In 

 the experiments of Butts and Deuel, ^*'' no sexual variation in fasting keto- 

 nuria was noted in the rat. The average ketonuria for the male rats 

 (based upon a 250 g. animal for four days), during two periods, amounted 

 to 5.5 and 7.5 mg., while the comparative results on females were 4.8 and 

 7.0 mg. Apparently, the sex variation in ketonuria does not obtain for 

 the fasting ketonuria in the rat, as it does for starvation ketosis in human 

 subjects. 



a'. Exogenous Ketonuria: Butts and DeueP^* reported that a physio- 

 logic ketonuria can be produced in rats if they are given orally, during fast- 

 ing, a solution of acetoacetate which has been adjusted to a pH of 7.40. 

 This ketonuria is reproducible in different animals, and the experiment can, 

 in most cases, be continued for fi\e or even seven days without fatality. 

 The most satisfactory dosage of sodium acetoacetate was found to be 150 

 mg. (calculated as acetone) per 100 sq. cm. of body surface per day, 

 given in divided doses in the morning and in the evening. Surface area 

 can be calculated by the formula of Lee,*^^ based upon the weight on the 

 first day of the test. Under usual conditions, no food is given during the 

 ketonuria test, but substances which are to be tested as sources of ketolytic 

 material are administered in appropriate dosages at the same time that the 

 ketogenic material is given. It is most important that a supply of water 

 be continuously available, as the animals must have a sufficient amount 

 because of the diuretic effect of the ketones. Urine collections can be made 

 in flasks connected with funnels above which round cages are suspended, 

 as described by Levine and Smith. ^^^ To prevent contamination of the 

 urine with feces, a cone made of wire netting is inserted in the neck of the 

 fxmnel. Urine is collected under paraffin oil to prevent the volatilization of 

 acetone. 



Although acetoacetate was administered in the early experiments 

 to produce the ketosis, ^'-^^^-^^^'^^^ it was later found that butyric acid was 

 eciually effective, and it has since been used in place of acetoacetate. Not 

 only is butyric acid cheaper, more uniform, and much more easily prepared 

 for use than is acetoacetate, but solutions of sodium butyrate are more 

 stable than are those of sodium acetoacetate. In the later tests by the 

 Deuel group and the Butts group and others, in which exogenous ketonuria 

 was employed to study the ketolytic action of various metabolites, sodium 

 butyrate was exclusively employed as the ketogenic agent. Because of the 



38U. S. Butts and H. J. Deuel, Jr., /. Biol. Chem., 100, 415-428 (1933). 



^ M. O. Lee, Am. J. Physiol, 89, 24-33 (1929). 



386 H. Levine and A. H. Smith, J. Lab. Clin. Med., 11, 1G8-172 (1925). 



