Characterization of growth hormone binding sites in the goldfish,Carassius auratus: effects of hypophysectomy and hormone injection |
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| Authors: | Yushi Zhang Tracy A Marchant |
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| Institution: | (1) Department of Biology, University of Saskatchewan, S7N 5E2 Saskatoon, Saskatchewan, Canada |
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| Abstract: | A recombinant carp growth hormone (rcGH) was used to develop for a GH radioreceptor binding assay in the goldfish (Carassius auratus). Specific binding of125I-rcGH to goldfish liver membranes was a pH, time, temperature, and membrane protein dependent process. Scatchard and LIGAND analysis indicated a single class of high affinity and low capacity binding site, with an association constant (Ka) of 1.9×1010 M–1 and a maximum binding capacity (Bmax) of 9 fmol mg–1 protein. Liver tissue displayed the highest125I-rcGH binding of all the tissues examined. Displacement of125I-rcGH with various unlabeled teleost and mammalian GHs and prolactins revealed that the goldfish hepatic binding site was highly specific for teleost GH. Intraperitoneal administration of 0.1, 1.0, and 10  g rcGH g–1 body weight to hypophysectomized goldfish resulted in a 27, 52, and 68% decrease in total binding sites, respectively. Injection of a high dose of rat prolactin (rPRL) (5 g rPRL g–1 body weight) also resulted in a 32% decrease in total binding sites. These results suggest that endogenous GH may have a role in the regulation of its own receptors in the goldfish. |
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| Keywords: | growth hormone receptor hypophysectomy liver goldfish teleost |
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