Ovine placental lactogen and human growth hormone bind to different regions of the same receptors.
Anti-human growth hormone (hGH) polyclonal and monoclonal antibodies (MAb) failed to recognize ovine placental lactogen (oPL), indicating that the antigenic topographies of both hormones are different. Binding assays showed that oPL completely inhibited hGH binding to lactogenic receptors from Nb2-cells and to somatogenic receptors from rabbit or sheep liver; in contrast, oPL only bound to a subpopulation of rat liver receptors. Zinc ion increased hGH and oPL binding to Nb2-cell receptors and slightly inhibited both hormones' recognition by somatogenic receptors. However, ZnCl(2) increased hGH binding to rat liver microsomes but prevented that of oPL. Furthermore, MAb R7B4, recognizing lactogenic as well as somatogenic receptors, entirely blocked hGH binding to the various receptor systems but not affected oPL binding. Therefore, results presented in this paper suggest that oPL and hGH bind to different regions of the same receptors.
Longhi
S A
SA
Instituto de Química y Fisicoquímica Biológicas (UBA-CONICET), Facultad de Farmacia y Bioquímica, Buenos Aires, Argentina.
Wolfenstein-Todel
C
C
Gómez
K A
KA
Miranda
M E
ME
Retegui
L A
LA
D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D001665:Binding Sites; D001667:Binding, Competitive / Q000187:drug effects; D002455:Cell Division / Q000502:physiology; D002462:Cell Membrane / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D019382:Human Growth Hormone / Q000378:metabolism*; D006801:Humans; D008223:Lymphoma / Q000378:metabolism / Q000473:pathology; D008862:Microsomes, Liver / Q000378:metabolism; D010920:Placenta / Q000737:chemistry*; D010928:Placental Lactogen / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects; D011817:Rabbits; D011863:Radioimmunoassay; D051381:Rats; D011981:Receptors, Prolactin / Q000378:metabolism*; D011986:Receptors, Somatotropin / Q000378:metabolism*; D012756:Sheep / Q000196:embryology*; D013053:Spectrophotometry; D015032:Zinc / Q000494:pharmacology
D000911:Antibodies, Monoclonal; D011981:Receptors, Prolactin; D011986:Receptors, Somatotropin; D019382:Human Growth Hormone; D010928:Placental Lactogen; D015032:Zinc