Human growth hormone deletion mutant (hGH44-191) binds with high affinity to lactogenic receptors but not to somatogenic receptors.
The carboxyl-terminal hGH fragment, hGH44-191, displays diabetogenic activity. To understand whether this biological activity is mediated through somatogenic or lactogenic receptors, we investigated the ability of hGH44-191 to bind both receptor classes. We found that hGH44-191 could not compete with [125I]hGH or [125I]bGH for bovine liver somatogenic binding sites. Additionally, hGH44-191 could not displace [125I]hGH from the somatogenic receptor sites when human liver microsomes were used as the receptor source. In contrast, hGH44-191 effectively competed with [125I]hGH for lactogenic receptor sites of lactating mammary gland microsomes and of bovine liver microsomes. In summary, hGH44-191 does not bind to somatogenic receptors but does not bind to lactogenic receptors. These data suggest that the biological actions of hGH44-191 could be mediated through lactogenic receptors.
Haro
L S
LS
Division of Life Sciences, University of Texas at San Antonio 78249, USA.
Singh
R N
RN
Lewis
U J
UJ
Martinez
A O
AO
Galosy
S S
SS
Staten
N R
NR
Krivi
G G
GG
D000818:Animals; D001665:Binding Sites; D002417:Cattle; D005260:Female; D013006:Growth Hormone / Q000302:isolation & purification / Q000378:metabolism*; D006801:Humans; D007457:Iodine Radioisotopes; D007700:Kinetics; D007774:Lactation; D008321:Mammary Glands, Animal / Q000378:metabolism*; D008861:Microsomes / Q000378:metabolism*; D008862:Microsomes, Liver / Q000378:metabolism*; D016296:Mutagenesis; D010446:Peptide Fragments / Q000378:metabolism*; D010902:Pituitary Gland / Q000378:metabolism; D011817:Rabbits; D011869:Radioligand Assay; D011974:Receptors, LH / Q000378:metabolism*; D011986:Receptors, Somatotropin / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D017384:Sequence Deletion
D007457:Iodine Radioisotopes; D010446:Peptide Fragments; D011974:Receptors, LH; D011986:Receptors, Somatotropin; D011994:Recombinant Proteins; C087514:somatotropin (44-191); D013006:Growth Hormone