THE PITUITARY GROWTH HORMONE 



377 



Stimulated the incorporation of the labeled carbon from these various 

 precursors into protein. 



We have recently found (Hotchkiss and Knobil, 1960) that insulin 

 added to diaphragms of hypophysectomized rats also increases the in- 

 corporation of carbon from labeled palmitate into protein, but growth 

 hormone added in vitro to the same system had no efifect ( Table VIII ) . 

 These experiments are preliminary, however, and provide but a start- 

 ing point for further study. 



The foregoing summary of our recent and current studies of the 

 action of growth hormone has omitted consideration of the influences 

 of this hormone on carbohydrate metabolism. These include an inhibi- 

 tion of glucose utilization on the one hand and an insulin-like or hypo- 

 glycemic effect on the other, depending on the experimental circum- 

 stances involved. There is no doubt that these effects are related to the 

 influence of growth hormone on lipid mobilization and synthesis, but 

 the nature of the relationship remains obscure, and nothing of conse- 

 quence relevant to these questions can now be added to the extensive 

 discussions that have recently appeared (de Bodo and Altzuler, 1957, 

 1958; Ketterer, Randle, and Young, 1957; Knobil and Creep, 1959; 

 Wertheimer and Shafrir, 1960 ) . 



The underlying metabolic and biochemical bases for the growth- 

 promoting activity of growth hormone remain to be elucidated. Much 

 more information is needed before meaningful working hyootheses 

 can be derived which will permit the synthesis of the great catalogue 

 of often seemingly unrelated facts that has been amassed to date. The 

 possibility that some of the effects ascribed to growth hormone may be 



Mean ± S.E.; number of observations in parentheses. 



