THE PITUITARY GROWTH HORMONE 



363 



lar concentration of a non-utilizable amino acid, a-amino-isobutyric 

 acid (AIB). More recently we have extended these studies to an in 

 vitro system employing the isolated "intact" diaphragm preparation of 

 Kipnis and Cori (1957). As illustrated in Figure 4, it was found that 

 hypophysectomy markedly decreases the penetration of labeled AIB 

 into the isolated diaphragm, while the addition of growth hormone to 

 the medium returns the transport of the amino acid to normal ( Kostyo, 



1.8 r 



1.6- 



1.4- 



0.4- 



Q.2 



40 60 80 



INCUBATION TIME 

 (MINUTES) 



100 



120 



Figure 4. Penetration of AIB-l-C^* into "intact" rat diaphragm preparations. 

 • normal; o hypophysectomized; A hypophysectomized + simian growth 

 hormone added to medium (25 /xgm/ml); D hypophysectomized + bovine 

 growth hormone added to medium (25 ^gm/ml). (From Kostyo, Hotchkiss, 

 and Knobil, 1959.) 



