Stimulation of amino acid transport in isolated diaphragm by growth hormone added in vitro.

The influence of the pituitary on the transport of alpha-aminoisobutyric acid-1-C(14) into the cells of isolated rat diaphragm was investigated. Hypophysectomy results in a lower-than-normal rate of alpha-aminoisobutyric acid-1-C(14) penetration into muscle. Adding either simian or bovine growth hormone preparations to the incubation medium in concentrations of 2.5 to 25 microg/ml of medium resulted in a doubling of the alpha-aminoisobutyric acid-l-C(14) penetration rate. The stimulatory effect was minimized when the hormone concentration was reduced to 0.25 microg/ml of medium.