Effect of enzyme and enzyme inhibitors on specific binding of hGH to human peripheral lymphocytes.
A recently described method to investigate growth hormone (GH) receptors on circulating human blood cells has been used to study the effect of a trypsin preparation and antitrypsin moieties on hormone binding to lymphocytes. Trypsinization with one defined dose of trypsin (10 ng/ml) led to a considerable decrease both of specific binding and of binding affinity (affinity constant after 60 min trypsinization 0.5 X 10(9) vs 1.5 X 10(9) M-1 in untreated control cells). Exposure of peripheral blood lymphocytes (PBL) to antitrypsin activities was followed by a steady increase of affinity and specific binding (affinity constant: with 10 KIU anti-trypsin 1.9 X 10(9) M-1, with 100 KIU 2.4 X 10(9) M-1, with 1000 KIU 3.6 X 10(9) M-1). This antitrypsin effect exceeds the binding values expected after blocking trypsin activities in the incubation medium. In a subset of experiments somatomedin-B (SM-B) was used as the antitrypsin moiety and was shown to increase specific GH binding to PBL in a similar manner as did antitrypsin (with 1000 ng SM-B affinity constant (Ka) 12.0 X 10(9) M-1, specific binding 9.7% of total radioactivity). It is concluded that enzymatic factors and their inhibitors including partially GH dependent moieties like SM-B modulate specific GH binding to human peripheral lymphocytes in vitro.
Kiess
W
W
Butenandt
O
O
D000328:Adult; D002478:Cells, Cultured; D003470:Culture Media; D006801:Humans; D008214:Lymphocytes / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000187:drug effects*; D011986:Receptors, Somatotropin; D013002:Somatomedins / Q000494:pharmacology; D013997:Time Factors; D014357:Trypsin / Q000494:pharmacology*; D014361:Trypsin Inhibitors / Q000494:pharmacology*
D003470:Culture Media; D011956:Receptors, Cell Surface; D011986:Receptors, Somatotropin; D013002:Somatomedins; D014361:Trypsin Inhibitors; C016756:somatomedin B; D014357:Trypsin