IMMUNOELECTROPHORETIC STUDIES OF RAT SOMATOMEDIN

Abstract

Serum was collected from hypophysectomized rat (HyR) 30 min. after an I.V. injection of hGH. The serum was used to prepare an antiserum (AS) in a rabbit. AS was adsorbed with lyophilized HyR serum (5 mg/ml) and centrifuged to obtain adsorbed antiserum (AAS). Immunoelectrophoresis (pH 9.5) using AS produced a number of lines with normal, HyR serum and Hy + hormone-treated serum but no line with hGH or insulin. AAS did not react with HyR serum but produced a single identical line (at beta globulin) with normal or Hy + GH treated serum. This precipitin line which was also present when whole AS was used may correspond to somatomedin produced in response to hGH. A similar and identical precipitin line was obtained with HyR + bGH treated serum but not with normal human serum. These results suggest that (1) hGH and bGH produce immunologically similar somatomedin(s) in the rat, (2) human somatomedin is immunologically different from rat somatomedin. This laboratory has already shown differences in the kinetics of bGH and hGH uptake by human liver slices.