Interaction between growth hormone and rat muscle in vitro

¹ Department of Physiology and Division of Endocrinology, Duke University Medical Center, Durham, North Carolina

Hypophysectomized rat diaphragms, which were immersed briefly in dilute solutions of growth hormone and then washed thoroughly, subsequently transported -aminoisobutyric acid-1-C¹⁴ at a greater rate than the controls. Growth hormones of bovine, porcine, simian and human origins were all effective. Increasing either the hormone concentration or the length of time that the diaphragms were immersed in growth hormone solutions increased the effect on amino acid transport. Prolonged washing of the diaphragms following exposure to growth hormone did not reduce the magnitude of the effect on amino acid transport. Moreover, reducing the temperature of the growth hormone solutions did not diminish the resultant effect on amino acid transport. From these results, it was concluded that the initial interaction between growth hormone and rat muscle in vitro occurs rapidly and the modification produced by this interaction is relatively stable.