622 VI. OCCURRENCE OF LIPIDS IN THE ANIMAL 



reported evidence of lipolytic activity in fatty tissues from the rat and 

 rabbit, but not in the fatty tissues of other animals. The results on human 

 fatty tissues have all shown definite lipolytic activity. 485-487 Renold and 

 Marble 487 demonstrated lipolytic activity in the subcutaneous adipose tis- 

 sue of both rat and man. On the other hand, human intra-articular fat 

 had only about 30% of the activity of human subcutaneous fat. More- 

 over, a sex variation in lipase activity obtained; in all cases, the concen- 

 tration of lipolytic enzymes in the adipose tissues of females exceeded that 

 in corresponding tissues from males. In cases of diabetes mellitus, the 

 male tissue had only one-fourth of the lipolytic activity of the correspond- 

 ing fatty tissue from women. 



In the case of rat adipose tissue, Renold and Marble 487 were unable to 

 demonstrate any correlation between lipolytic activity and sex, age, or food 

 intake. Brown fat from a young rat had a lower lipase content than did 

 white fat. The lipolytic activity of rat adipose tissue was one-third of that 

 of the pancreas and one-half that of the liver. 



Shapiro and Wertheimer 421 have shown that enzymes capable of attack- 

 ing phospholipids, glycerophosphoric acid, lactic acid, and succinic acid are 

 present in adipose tissue extracts. 



(7) Brown vs. White Adipose Tissue 



Distinct differences obtain both qualitatively and quantitatively between 

 brown and white adipose tissue. 488 Brown adipose tissue occurs in the 

 adult mouse and rat, and in human embryos, 488 but it is not present in the 

 rabbit, except in the embryonic form. 401 White fatty tissue, largely de- 

 pleted of its fat, has properties similar to those of brown fat tissue ; it also 

 resembles the latter tissue morphologically. Wertheimer and Shapiro 401 

 suggest that brown adipose tissue may be considered to be embryonic tissue 

 which has failed to develop further in postnatal life. 



Eger 488 showed that brown tissue has a much higher metabolic activity 

 than does its white counterpart. Moreover, it has been shown to store 

 glycogen in much higher concentrations than does white adipose tissue; 

 values for fatty tissue glycogen comparable with those of the liver have been 

 reported by Tuerkischer and Wertheimer. 120 On the other hand, 

 Clement 489 reported that fat mobilization is considerably depressed in brown 

 adipose tissue. 



486 D. L. Oesterreicher, Thesis, Univ. Western Ontario, 1947; cited by A. E. Renold 

 and A. Marble, J. Biol. Chem., 185, 367-375 (1950), p. 367. 



486 A. Marble and R. M. Smith, Proc. Am. Diabetes Assoc, 2, 173-186 (1942). 



487 A. E. Renold and A. Marble, J. Biol. Chem., 185, 367-375 (1950). 



488 E. Eger, Klin. Wochschr., 17, 1033-1038 (1938). 



489 G. Clement, Compt. rend. soc. biol, 141, 255-257 (1947). 



