The human liver growth hormone receptor.
Human livers, obtained from donors at the time of transplant, were homogenized in 0.25 M sucrose and fractionated by differential centrifugation. The specific binding of [125I] human (h) GH to total particulate fractions from 18 livers varied from 0.4-5.1% of the total radioactivity/100 micrograms protein. Binding affinity was 2.0 +/- 0.3 X 10(9) M-1, and binding capacity ranged from 14-53 fmol/mg protein. A different proportion of receptors occupied by endogenous hGH did not explain the large variation in binding. Binding sites were specific for hGH. Dissociation of the hormone-receptor complex was extremely slow. No specific binding of [125I]hPRL was observed. Specific binding of insulin was found in fractions from all livers and varied less than hGH binding. Cross-linking of [125I]hGH to plasma membrane and microsome receptors yielded two major autoradiographic bands corresponding to an estimated mol wt of 103,000 for the receptor, with a possible subunit of 54,000. Human liver primary fractions were characterized. The binding of hGH and insulin displayed a nucleo-microsomal distribution pattern in the primary fractions; 54.2% and 27.9% of the hGH-binding activity were found in the microsomes and the nuclear fraction, respectively, whereas insulin binds equally to nuclear and microsomal elements. Our findings suggest that hGH-binding sites are present in the plasma membrane and also in one or more intracellular compartments, whereas a high proportion of insulin receptors is associated with the plasma membrane.
Hocquette
J F
JF
Unité de Biologie et Pathologie de la Croissance et du Développement, INSERM U.30, Hôpital des Enfants Malades, Paris, France.
Postel-Vinay
M C
MC
Kayser
C
C
de Hemptinne
B
B
Amar-Costesec
A
A
D001665:Binding Sites; D003432:Cross-Linking Reagents; D013006:Growth Hormone / Q000378:metabolism*; D006801:Humans; D007328:Insulin / Q000378:metabolism; D008099:Liver / Q000378:metabolism* / Q000648:ultrastructure; D008861:Microsomes / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism*; D013347:Subcellular Fractions / Q000378:metabolism; D014018:Tissue Distribution
D003432:Cross-Linking Reagents; D007328:Insulin; D011956:Receptors, Cell Surface; D013006:Growth Hormone