PARS GLANDULARIS AND METABOLISM 



previous work, indicates that hypophysectomy leads to the 

 following changes in the metabolism of carbohydrates.'^ 



1. The rate of absorption of glucose is abnormally slow. 



2. Fasting leads to an abnormally rapid utilization of glycogen both of 

 the liver and of striated muscle. The more labile hepatic glycogen is more 

 strikingly depleted. In the opinion of Fisher, Russell, and Cori (1937), a 

 secretion of the pars glandularis regulates the (formation and) utilization 

 of glycogen in fasting animals and spares carbohydrates so that fat and 

 protein are utilized to a greater extent as sources of energy. This regula- 

 tory influence is lost after removal of the gland, so that carbohydrate 

 oxidation continues at an abnormally rapid rate until even the concentra- 

 tion of sugar in the blood falls to low levels. 



3. A further metabolic abnormality probably is an interference with 

 gluconeogenesis from non-carbohydrate sources. It appears that the 

 glycerol of fats cannot be used to form carbohydrate in hypophysectomized 

 animals. The degree of disturbance of gluconeogenesis from proteins is 

 not known with any accuracy. Apparently glycine can be utilized. Also, 

 Fisher, Russell, and Cori found that the excretion of nitrogen in the urine 

 is not affected by hypophysectomy. However, the G/N ratio of hy- 

 pophysectomized dogs receiving phlorhizin is lower than normal and the 

 quantity of N excreted is less (Houssay and others), which suggest a 

 lowered rate of formation of glucose from protein. 



4. All the foregoing changes help to explain the slow rate at which carbo- 

 hydrate reserves are replenished when food is again furnished to fasting 

 hypophysectomized animals. Absorption is slow; the reserves are low or, 

 in the case of the liver, may be virtually exhausted; the animal continues 

 to depend to an abnormal extent on carbohydrate-oxidation as a source of 

 energy; and, finally, carbohydrate from non-carbohydrate sources can be 

 secured only to a limited extent. 



The effects of epinephrine in hypophysectomized animals. — 

 So far as carbohydrate metabolism in normal animals is con- 

 cerned, epinephrine appears to produce the following changes: 



I. A hyperglycemia appears and persists. The increased concentration 

 of blood sugar is partly due to increased hepatic glycogenolysis and part- 

 ly due to diminished utilization of sugar by the tissues. 



a. Simultaneously epinephrine promotes the formation of glycogen in 

 the liver from lactic acid, the formation of which depends upon the deg- 

 radation of muscle glycogen. In the formation of lactic acid from mus- 

 cle glycogen, hexosemonophosphate must be formed; phosphate is there- 

 fore mobilized, and the concentration of inorganic P in the blood falls. 



■5 The most numerous experiments have been performed with rats in which, as 

 Fisher, Russell, and Cori emphasize, experimental procedures such as fasting may 

 produce changes different from those observed in larger animals. 



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