An in vitro Action of Human Growth Hormone in the Presence of Actinomycin D

Protein Synthesis and Translational Control: A Historical Perspective

Protein synthesis and its regulation are central to all known forms of life and impinge on biological arenas as varied as agriculture, biotechnology, and medicine. Otherwise known as translation and translational control, these processes have been investigated with increasing intensity since the middle of the 20th century, and in increasing depth with advances in molecular and cell biology. We review the origins of the field, focusing on the underlying concepts and early studies of the cellular machinery and mechanisms involved. We highlight key discoveries and events on a timeline, consider areas where current research has engendered new ideas, and conclude with some speculation on future directions for the field.

Requirement of tyrosine residues 333 and 338 of the growth hormone (GH) receptor for selected GH-stimulated function

We have examined the involvement of tyrosine residues 333 and 338 of the growth hormone (GH) receptor in the cellular response to GH. Stable Chinese hamster ovary (CHO) cell clones expressing a receptor with tyrosine residues at position 333 and 338 of the receptor substituted for phenylalanine (CHO-GHR1-638 Y333F, Y338F) were generated by cDNA transfection. Compared with the wild type receptor the Y333F,Y338F mutant possessed normal high affinity ligand binding, hormone internalization, and ligand-induced receptor down-regulation. GH activation of mitogen-associated protein kinase was also similar in CHO clones expressing similar wild type and Y333F,Y338F receptor number. However, two GH-regulated cellular events (lipogenesis, and protein synthesis) were deficient in the tyrosine substituted receptor. In contrast, transcriptional regulation by GH (as evidenced by chloramphenicol acetyltransferase cDNA expression driven by the GH-responsive region of the SPI 2.1 gene) was not affected by Y333F,Y338F substitution. Thus we provide the first experimental evidence that specific tyrosine residues of the GH receptor are required for selected cellular responses to GH.

Conventional and nonconventional uses of growth hormone

Although GH has been available as a therapeutic agent for the GH-deficient child for more than 30 years, the conditions of its use have yet to be optimized. The availability of biosynthetic material has provided researchers with the opportunity to develop the protocols necessary to begin to finally answer the most fundamental questions pertaining to dose, frequency, and duration of treatment. It has also permitted the initiation of prospective trials in a large number of conditions that result in childhood short stature, with the expectation that some or many of them will be treated effectively and safely. Finally, it has opened the door to an entire spectrum of potentially new uses of GH and other growth factors for so-called nonconventional indications. That these have implications that range from the short-term rapid healing of a burn graft site, to the more efficient induction of ovulation, to the long-term preservation of lean body mass has excited the interest of investigators in many fields of medicine and physiology. Thus, the recent progress reported in this paper is really the beginning of the new research that will take place with GH and growth factors.

In vivo and in vitro effects of growth hormone on the incorporation of [14C]leucine into protein of liver and muscle of the eel

In vivo administration of ovine GH (2 micrograms/g body wt) increased [14C]leucine incorporation into protein of the liver, skeletal muscle, and opercular muscle of hypophysectomized eels. Addition of ovine GH into the medium (5 micrograms/ml) slightly increased [14C]leucine incorporation into protein of liver slices during 5 hr in vitro incubation, but did not affect protein synthesis from [14C]leucine in opercular muscle. In vivo pretreatment with ovine GH (2 micrograms/g body wt) 48 hr prior to tissue preparation clearly increased [14C]leucine incorporation into protein of liver slices in vitro. However, no statistically significant change was observed for in vitro incorporation of [14C]leucine into protein of opercular muscle of hypophysectomized eels which had been previously treated with ovine GH (2 micrograms/g body wt). These results indicate that ovine GH has a protein anabolic action in the liver and muscle of the eel and that compared to mammals a rather long lag period is needed to elicit such protein anabolic actions of GH in these animals.

Growth hormone: species-specific stimulation of erythropoiesis in vitro

The effects of purifed bovine and human growth hormone were tested in vitro with murine and human bone marrow by means of granulocyte-monocyte and erythroid progenitor cloning techniques. Nanogram concentrations of the growth hormones potentiated erythropoietin-stimulated erythropoiesis, but not granulopoiesis, in a species-specific manner.