198 III. OXIDATION AND METABOLISM 



(6) The Utilization of Ketone Bodies by Extrahepatic Tissues. Muscles 

 and other extrahepatic tissues can brmg about an oxidation of the 

 ketone bodies to carbon dioxide and water, thus obtaining the maximum 

 energy yield. According to Stadie,- the rate at which ketone bodies can be 

 utilized by the tissues of various animals is in the neighborhood of 3000 /iM 

 per 100 gm. per day. Marriott,^^* and Snapper and Griinbaum^^^ have 

 shown that the capacity of the tissues to utilize the ketone bodies is high. 

 Proof that these substances can be metabolized in tissues other than the 

 liver was adduced by Chaikoff and Soskin,^^* who observed that diacetic 

 acid injected into the depancreatized dog disappeared even after hepatec- 

 tomy. The latter workers demonstrated that the rate of utilization of 

 ketone bodies is a function of their level in the blood. Thus, while a high 

 rate of disappearance of ketone bodies by depancreatized, hepatectomized 

 dogs, which had also been nephrectomized, was noted when the plasma 

 level of ketone bodies was 100 mg. % and the blood ketone values rapidly 

 dropped to 20 to 30 mg. % there was a tendency toward leveling off at 

 this lower level. This would suggest that the rate of utilization of ketones 

 is very high where high blood ketone levels exist, but that the rate is 

 not of any great magnitude when the ketone levels are those ordinarily 

 obtained in ketosis. The results of Dye and Chidsey,^"'* as well as those of 

 Blixenkrone-M0ller,™ both support this conclusion. Nelson and collabora- 

 I^Qj.g68o likewise reported a relationship between the concentration of /3-hy- 

 droxybutyrate in the blood and its rate of oxidation. Mirsky^'*^ and Mirsky 

 and Broh-Kahn™'' reported the utilization of ketone bodies in blood from 

 eviscerated dogs and rabbits. Harrison and Long^^^ observed that |(3-hy- 

 droxybutyrate was removed from the blood by the muscles of rats which 

 had been fasted, or given anterior pituitary extract or phlorhizin, at the 

 same rate as by those of normal animals. Barnes et al?^'' and Waters and co- 

 workers^^^ noted the disappearance of the ketone bodies in the perfusing 

 solution of heart-lung preparations. 



Since the rate of utilization of ketone bodies by the extrahepatic tissues 

 appears to be little influenced by diabetic conditions, it is believed that 

 combustion of carbohydrate is not a prerequisite for their oxidation. Thus, 

 the utilization of ketone bodies was reported in depancreatized dogs by 

 Chaikoff and Soskin,"^ and in those of Bhxenkrone-M0ller,'^'^^ in phlorhizin- 



"" W. McK. Marriott, /. Biol Chem., 18, 241-262 (1914). 

 704 J. A. Dye and J. L. Chidsey, Am. J. Physiol., 127, 745-750 (1939). 

 TO5N. Blixenkrone-M0ller, Z. physiol. Chem., 253, 2G1-275 (1938). 

 ™ I. A. Mirsky and R. H. Broh-Kahn, Am. J. Physiol, 120, 446-450 (1936). 

 ™7 R. H. Barnes, E. M. MaoKay, G. K. Moe, and M. B. Visscher, Am. J. Physiol, 123, 

 272-279 (1938). 



