Autoradiographic localization of growth hormone binding sites in Sparus aurata tissues using a recombinant gilthead seabream growth hormone

Abstract

Growth hormone (GH) binding sites in tissues of gilthead seabream, Sparus aurata, were localized by using an in vitro autoradiographic analysis. Cryomicrotome sections of liver, spleen, kidney, heart and skeletal muscle were mounted on gelatin-coated slides and incubated with a radioiodinated recombinant gilthead seabream GH (0.54 ng/100 μl buffer) for 24 h at 4 °C. Slides were coated with autoradiographic emulsion and exposed for 1–9 weeks. The highest density of GH binding sites was found in liver. This specific binding was evident on hepatocytes. Blood cells in hepatic vascular system also showed GH binding while intrahepatic exocrine pancreas did not. In spleen, a high density of GH binding sites was found surrounding melanomacrophage centers. Splenic ellipsoid cells also showed a strong GH binding while splenic pulp exhibited a weak GH binding. Kidney GH binding sites were present in renal tubules and renal haemopoietic tissue. Cardiac muscle exhibited an intense GH binding. However, GH binding sites were not detected in body skeletal muscle. This study confirms and extends, by using autoradiographic techniques, previous results obtained by radioreceptor assays.