Stimulation of insulin-like growth factor-I production by recombinant bovine growth hormone in Mozambique tilapia, Oreochromis mossambicus |
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Authors: | S Kajimura K Uchida T Yada LG Riley JC Byatt RJ Collier K Aida T Hirano EG Grau |
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Institution: | (1) Department of Zoology and Hawaii Institute of Marine Biology, University of Hawaii, P.O. Box 1346, Kaneohe, HI 96744, USA;(2) Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo 113-8657, Japan;(3) Animal Agricultural Group, Monsanto, St. Louis, MO 63198, USA;(4) Department of Animal Science, University of Arizona, Tucson, AZ 85721, USA;(5) Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo 113-8657, Japan |
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Abstract: | We have previously reported growth-promoting effects of recombinant bovine growth hormone (rbGH) in Mozambique tilapia, Oreochromis mossambicus, after 4 weekly injections or a single injection of slow-releasing formulation (Posilac®) (Leedom et al. 2002). In order to obtain further understanding of the role of the growth hormone (GH)-insulin-like growth factor-I (IGF-I) axis in growth in the tilapia, the effects of rbGH on plasma and mRNA levels of IGF-I were examined. Plasma IGF-I levels were significantly increased after rbGH and Posilac® injections, and a significant correlation was observed between plasma IGF-I levels, body length and mass in both treatments. IGF-I mRNA levels in the liver and in the skeletal muscle were also significantly increased after rbGH and Posilac® injections, indicating that IGF-I gene expression in these tissues is under control of circulating GH. IGF-I mRNA levels in the gill were not affected by treatment. Liver IGF-I mRNA levels were significantly correlated with body length and with body mass after rbGH and Posilac® injections. These results indicate that the growth-promoting effect of rbGH in this species is mediated to a significant extent via its stimulation of hepatic production of IGF-I and the resulting increase in plasma IGF-I, and also possibly through locally produced IGF-I in the skeletal muscle, acting in a paracrine or autocrine fashion. |
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Keywords: | growth hormone insulin-like growth factor-I Oreochromis mossambicus RNase protection assay tilapia |
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