250 METABOLIC HORMONES 



Insecta. The secretion of the corpora allata stimulates the 

 anabolism of such organic phosphates as the mono- and di- 

 phosphoric hexose esters, which are not formed in its absence. 

 This metabohsm-stimulating function may be compared with the 

 increase in oxygen consumption caused by the same hormone in 

 Calliphora and elsewhere among insects (§ 5.111). It is a rather 

 different type of reaction from the translocation of phosphates 

 associated with calcium in crustaceans and vertebrates, nor is there 

 apparently any such calcium change in insects. 



Removing the corpora allata from developmental stages of 

 Carausius results in a decrease in the organic phosphates in both 

 the blood and the tissues relative to mineral phosphates (L'Helias, 

 1954). The difference between allatectomized and control 

 specimens is greatest in the 5th intermoult period and is 

 least in the "adultoid" stage, after the 7th moult, when the 

 corpora allata might be expected to be inactive in the controls 

 (cf. Part II, § 3). 



Vertebrata. There appears to be no clear-cut evidence on the 

 action of any hormone that increases blood phosphates, except in 

 mammals. Rasquin and Rosenbloom (1954) have discussed the 

 possibility of cortical control in fish, but have brought forward no 

 direct evidence for it (§ 5.411). 



Mammalia. It appears from experiments on rats that thyroxine 

 causes a direct increase in the level of phosphates in the blood. 

 The action is masked to some extent in both intact and thyroid- 

 ectomized controls, since the rise in phosphates induced by 

 thyroxine injection quickly stimulates secretion by the parathy- 

 roids, and the phosphate level is thereby restored to normal 

 (Engfeldt and Hjerquist, 1952). The action of the adrenal cortex, 

 when stimulating protein catabolism, also increases P as well as 

 N in the blood, at least until the balance is restored by the resulting 

 increase in parathormone secretion (§ 5.422). The opposing claim, 

 that injections of a cortisone-like hormone of the adrenal cortex 

 can lower the maximal amount of phosphate ions reabsorbed by 

 the kidney tubules (Roberts and Pitts, 1953) and can increase the 

 amount excreted, is probably therefore based on observations of 

 an indirect effect, due to the stimulation of the parathyroids. 



