PHYSIOLOGY OF ADIPOSE TISSUE 613 



onstrated that the fats in the fatty livers produced in mice by the injec- 

 tion of extracts of the anterior pituitary gland had been transported to that 

 organ from the adipose storage depots. The identity of the specific hor- 

 mone responsible for this fat-mobilizing action is not entirely established. 

 Best and Campbell 434 prepared a fat-mobilizing hormone from the anterior 

 pituitary which, when injected into fasted mice, increased the quantity of 

 liver fat linearly with the dose administered. This was called adipokinin. 435 

 It was subsequently shown that this product increases not only liver lipid 

 but also that in the kidney. 436 Its mobilizing action is confined to the glyc- 

 eride portion of the fat, and the amount of lipid transferred is a function of 

 the glyceride content of the fat depots. 436 



If adipokinin is a separate entity among the hormones of the anterior 

 pituitary gland, its fat-mobilizing action is shared by other pituitary hor- 

 mones. Thus, Dobyns 437 reported the complete exhaustion of fat from the 

 fat depots of mice and its replacement by a gelatinous material when the 

 thyrotropic hormone of the anterior lobe of the pituitary was injected. 

 Since this effect was noted even in the absence of the thyroid gland, it may 

 indicate that the action was due to an impurity in the preparation of the 

 thyrotropic hormone. It might likewise suggest that this hormone had a 

 dual action. According to Reiss, 438 the lactogenic hormone of the anterior 

 lobe of the pituitary also reduces the fat content of adipose tissue in the rat 

 and in man. It is altogether possible that this may be a physiologic reac- 

 tion which aids in providing fat during the lactation process. It is thus 

 uncertain whether adipokinin, the thyrotropic hormone, and the lactogenic 

 hormone, are all active as fat-mobilizing agents, or whether adipokinin 

 alone is active. Under the latter conditions, the positive response of other 

 anterior pituitary hormones would be the result of an impurity in the adi- 

 pokinin. 



There is a definite indication that such fat-mobilizing hormones play a 

 role in normal metabolism. Weil and Stetten 435 isolated a component, 

 capable of increasing the liver lipid in the mouse, from the urine of fasted 

 but not from that of normally fed rabbits. It is not known whether or not 

 this material is adipokinin. However, it resembles the latter compound in 

 that it is precipitable at pH 5.2 by 2 volumes of ethanol. 



The mechanism by which pituitary hormones invoke fat mobilization 

 would seem to be connected with a nerve stimulation of the adipose tissues. 



434 C. H. Best and J. Campbell, /. Physiol. 86, 190-203 (1936). 



435 R. Weil and De W. Stetten, Jr., J. Biol. Chem., 168, 129-132 (1947). 



436 J. Campbell and C. C. Lucas, Biochem. J., 48, 241-245 (1951). 



437 B. M. Dobyns, Surg. Gynecol. Obstet., 82, 609-617, 717-722 (1946). 



438 M. Reiss, Endocrinology, 40, 294-298 (1947). 



