Chronic effects of equine growth hormone (cGH) on insulin-like growth factor (IGF)-I and IGF binding proteins (IGFBP) in mares

R. A. Christensen, S. V. Radecki, K. Malinowski, C. G. Scanes, H. D. Hafs

Research output: Contribution to journalArticlepeer-review

Abstract

Mares aged 18 to 25 yr were given daily sc injections of eGH (6.25 or 12.5 mg; n = 5 or 6) for 6 wk. Plasma eGH and IGF-I were determined by RIA in blood sampled weekly immediately before cGH injections. Plasma proteins were separated by SDS-PAGE and IGFBP were quantified by densitometry of ligand blots on PVDF membranes. From weeks 0 to 6, plasma GH increased (P < .05) from 1.5 to 7.4 ng/ml for mares given 6.25 mg eGH, and from 2.9 to 10.6 ng/ml for mares given 12.5 mg eGH. Plasma GH at 2 wk following the final eGH injection (4.6 and 5.9 ng/ml, respectively) remained above (P < .05) pretreatment values. Plasma IGF-1 more than doubled (P < .05) within 1 wk of eGH injections, plateaued from wk 4 to 6 at values 2.5- to 3fold higher than pretreatment values, but approached the pretreatmenl values within 2 wk after eGH injections ceased. Six IGFBP (26, 39, 46, 48, 97 and 107 kDa) were identified, of which the larger four increased (P < .05) during the 6-wk eGH injection period. We conclude that the IGF-I axis is responsive to exogenous eGH in aged mares. (Supported by the NJ Equine Research Initiative and Brcsatec Ltd., Adelaide, Australia.).

Original languageEnglish (US)
Pages (from-to)A769
JournalFASEB Journal
Volume10
Issue number3
StatePublished - 1996

All Science Journal Classification (ASJC) codes

  • Biotechnology
  • Biochemistry
  • Molecular Biology
  • Genetics

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