GROWTH HORMONE (GH) REGULATION OF GH RECEPTOR AND MEMBRANE ASSOCIATED-GH BINDING PROTEIN.

AI SOTELO; CURTO L.M.; L GONZALEZ; A BARTKE

Denver

Congreso; XXXIII Reunión anual de la Endocrine Society, ENDO 2001.; 2001

Growth hormone has been known to induce its own receptor levels, however, regulation of growth hormone receptor concentration had been studied by radio-labeled GH binding to membranes. Recently, it was described for the mouse that most of that binding was accounted for by growth hormone binding protein associated to membranes. We have used mice models that do not express GH and transgenic mice that over-express growth hormone, as well as a GH antagonist, to study the effect of different GH levels on GHR and on MA-GHBP by means of specific radioimmunoassays.In absence of GH, as well as in presence of high antagonist concentration, GHR and MA-GHBP levels are slightly lower than normal controls. For moderate levels of GH, GHR and MA-GHBP increase in a similar fashion. But for high GH concentrations, the rise in MA-GHBP leves is much more important than that of GHR. It si concluded that, by inducing a higher rise in MA-GHBP levels, GH would produce a down-regulation of its own action, since MA-GHBP would inhibit ligand-induced receptor dimerization ((GHR)2:GH) needed for biological action.