Co-Authors:
Ashkenazi, A., Department of Biochemistry and Human Nutrition, Hebrew University of Jerusalem, Biotechnobgy General (Israel) Ltd., Rehovot, Israel
Vogel, T., Department of Biochemistry and Human Nutrition, Hebrew University of Jerusalem, Biotechnobgy General (Israel) Ltd., Rehovot, Israel
Barash, I., Department of Biochemistry and Human Nutrition, Hebrew University of Jerusalem, Biotechnobgy General (Israel) Ltd., Rehovot, Israel
Hadari, D., Department of Biochemistry and Human Nutrition, Hebrew University of Jerusalem, Biotechnobgy General (Israel) Ltd., Rehovot, Israel
Levanon, A., Department of Biochemistry and Human Nutrition, Hebrew University of Jerusalem, Biotechnobgy General (Israel) Ltd., Rehovot, Israel
Gorecki, M., Department of Biochemistry and Human Nutrition, Hebrew University of Jerusalem, Biotechnobgy General (Israel) Ltd., Rehovot, Israel
Gertler, A., Department of Biochemistry and Human Nutrition, Hebrew University of Jerusalem, Biotechnobgy General (Israel) Ltd., Rehovot, Israel
Abstract:
A modified analog of human GH (hGH), prepared by recombinant DNA technology, that lacks 13 amino acids at the amino terminus (Met14 hGH), was able to compete with [125I]hGH for binding to lactogenic receptors in Nb2-llC rat lymphoma cells, to somatotropic receptors in IM-9 human lymphocytes, and to both lactogenic and somatotropic receptors in the microsomal fraction of virgin female rat liver. Exposure of intact Nb2 or IM-9 cells to Met14hGH did not reduce the number of surface or intracellular receptors, as compared to the control without hormone. A parallel exposure to 500-fold lower concentrations of hGH resulted in 77–93% reduction in both surface and intracellular receptors. In contrast to [125I]hGH, [125I]Met uhGH was not taken up by the intact Nb2 lymphoma cells. Infusion of anesthetized female virgin rats for 3 h with hGH down-regulated both lactogenic and somatotropic receptors in the liver. A similar infusion with up to 200-fold higher amounts of MetI4hGH did not lower the number of total receptors, indicating lack of down-regulation. Some decrease in the binding to free receptors was observed, suggesting that Met14hGH is capable of binding to liver receptors in vivo. © 1987 by The Endocrine Society.