Abstract

The effect of bovine growth hormone (BGH) upon intracellular accumulation and incorporation of L-leucine-1-¹⁴C and L-tyrosine-¹⁴C (uniformly labeled) into protein was studied in vitro in the diaphragm of the hypophysectomized rat. Amino acid uptake apparently was not stimulated at any time up to 90 min, whereas stimulation of incorporation into protein was noted after 40 min. BGH given between 44 and 4 hr before the rats were killed did not cause in vitro stimulation of uracil-2-¹⁴C incorporation into total nucleic acids of the hypophysectomized rat diaphragm. Actinomycin D partially inhibited L-leucine-1-¹⁴C incorporation into protein, and inhibited by 95% the incorporation of adenine-8-¹⁴C into nucleic acids. In the presence of actinomycin D, BGH stimulated L-leucine incorporation into protein but did not affect adenine-8-¹⁴C incorporation into nucleic acids. Thus, BGH stimulation of amino acid incorporation may not be dependent upon an increase in intracellular amino acid accumulation or a stimulation of RNA synthesis in vitro.