| Reference | [1]. J Endocrinol. 2005 Apr;185(1):197-206. doi: 10.1677/joe.1.06037.<br />
Production of recombinant porcine IGF-binding protein-5 and its effect on proliferation of porcine embryonic myoblast cultures in the presence and absence of IGF-I and Long-R3-IGF-I.<br />
Pampusch MS(1), Xi G, Kamanga-Sollo E, Loseth KJ, Hathaway MR, Dayton WR, White ME.<br />
Author information: (1)Animal Growth and Development Laboratory, Department of Animal Science, University of Minnesota, St Paul, Minnesota 55108, USA.<br />
IGF-binding protein-5 (IGFBP-5) is produced by porcine embryonic myogenic cell (PEMC) cultures and is secreted into the medium. IGFBP-5 may play some role in myogenesis and/or in changes in myogenic cell proliferation that accompany differentiation. IGFBP-5 reportedly may either suppress or stimulate proliferation or differentiation of cultured cells depending on cell type and culture conditions. Additionally, IGFBP-5 has been shown to possess both IGF-dependent and IGF-independent actions in some cell types. The goal of this study was to produce recombinant porcine IGFBP-5 (rpIGFBP-5) and assess its IGF-I-dependent and IGF-I-independent actions on the proliferation of PEMCs. To accomplish this, we have expressed porcine IGFBP-5 in the baculovirus system, purified and characterized the expressed rpIGFBP-5 and produced an anti-porcine IGFBP-5 antibody that neutralizes the biological activity of porcine IGFBP-5. rpIGFBP-5, purified to 98% homogeneity using nickel affinity chromatography and IGF-I affinity chromatography, suppressed IGF-I-stimulated proliferation of PEMCs in a concentration-dependent manner (P>0.05). rpIGFBP-5 also suppressed Long-R3-IGF-I-stimulated proliferation of PEMCs (P>0.05), even in the presence of significant molar excess of Long-R3-IGF-I compared with rpIGFBP-5, demonstrating the IGF-independent activity that rpIGFBP-5 possesses in PEMCs, since Long-R3-IGF-I is an IGF analog that has very low affinity for the IGFBPs but retains its ability to bind to the type I IGF receptor and thereby can stimulate proliferation. The anti-rpIGFBP-5 IgY produced against rpIGFBP-5 specifically recognized native porcine IGFBP-5 in PEMC media that also contained porcine IGFBP-2, -3, and -4. This antibody is capable of neutralizing the effects of both rpIGFBP-5 and endogenously produced porcine IGFBP-5 on PEMCs as well as detecting IGFBP-5 in Western blots. The production of rpIGFBP-5 and a neutralizing antibody to porcine IGFBP-5 provides a powerful tool to investigate the role of IGFBP-5 in porcine myogenic cell proliferation and differentiation. The data provided here demonstrated that IGFBP-5 has the potential to affect proliferation of PEMCs during critical periods of in vitro muscle cell development and therefore may impact the capacity for ultimate postnatal muscle mass development in vivo.<br />
DOI: 10.1677/joe.1.06037 PMID: 15817840<br />
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[2]. Am J Physiol. 1997 Jul;273(1 Pt 1):E130-8. doi: 10.1152/ajpendo.1997.273.1.E130.<br />
The somatotropic axis in neonatal calves can be modulated by nutrition, growth hormone, and Long-R3-IGF-I.<br />
Hammon H(1), Blum JW.<br />
Author information: (1)Division of Nutrition Pathology, University of Bern, Switzerland.<br />
Effects on the somatotropic axis [plasma levels of insulin-like growth factors (IGFs) I and II, IGF-binding proteins (IGFBPs), and growth hormone (GH)] of feeding different amounts of colostrum or milk replacer, of Long-R3-IGF-I (administered subcutaneously or orally; 50 micrograms.kg body wt-1.day-1 for 7 days), and of subcutaneously injected recombinant bovine GH (rbGH; 1 mg.kg body wt-1.day-1 for 7 days) were evaluated in calves during the 1st wk of life. Plasma Long-R3-IGF-I increased after subcutaneous application but not with the oral dose. Endogenous IGF-I was higher in calves fed colostrum six times compared with those fed only milk replacer. Native IGF-I was highest in rbGH-injected calves but was lowered by the subcutaneous injection of Long-R3-IGF-I. IGF-II concentrations were not modified by any of the treatments. IGFBP-2 increased in calves fed only milk replacer and those receiving subcutaneous Long-R3-IGF-I. GH was not modulated by differences in nutrition but increased after rbGH administration and similarly in all groups after intravenous injection of GH-releasing factor analog GRF-(1-29). Parenteral administration of Long-R3-IGF-I decreased GH concentration but did not affect the secretory pattern. The data demonstrate that the somatotrophic axis is basically functioning in neonatal calves and is influenced by nutrition, GH, and Long-R3-IGF-I.<br />
DOI: 10.1152/ajpendo.1997.273.1.E130 PMID: 9252489<br />
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[3]. J Endocrinol. 1995 Aug;146(2):247-53. doi: 10.1677/joe.0.1460247.<br />
Long R3 insulin-like growth factor-I (IGF-I) infusion stimulates organ growth but reduces plasma IGF-I, IGF-II and IGF binding protein concentrations in the guinea pig.<br />
Conlon MA(1), Tomas FM, Owens PC, Wallace JC, Howarth GS, Ballard FJ.<br />
Author information: (1)Department of Biochemistry, University of Adelaide, Australia.<br />
We have tested whether an animal with substantial amounts of both IGF-I and IGF-II in circulation, such as the guinea pig, would respond to chronic IGF infusion in the same manner as the adult rat, which has negligible amounts of IGF-II in blood. Female guinea pigs of 350 g body weight were continuously infused for 7 days with recombinant guinea pig IGF-I or -II (120 or 360 micrograms/day) or long R3 IGF-I (LR3IGF-I) (120 micrograms/day), an analogue which has much reduced affinities for IGF binding proteins. IGF-I or IGF-II infusion led to substantial increases in plasma IGF-I or IGF-II respectively in comparison with vehicle-infused animals. Nevertheless, body weight gain, feed intake, feed conversion efficiency and carcass composition were not significantly affected by any treatment (significance was deemed to be P < 0.05). Amongst the tissues examined only the fractional weight (g/kg body weight) of the adrenals was increased, and that only by the higher dose (360 micrograms/day) of IGF-I. However, the fractional weight of adrenals, gut, kidneys and spleen were significantly increased by LR3IGF-I, but again overall growth was not stimulated. A possible explanation for the lack of IGF-I effects is that total circulating IGF concentrations were not increased by these treatments. IGF-II significantly raised total IGF concentrations at the higher dose only. Plasma IGF-I was reduced by IGF-II infusion, as was plasma IGF-II by IGF-I infusion.(ABSTRACT TRUNCATED AT 250 WORDS)<br />
DOI: 10.1677/joe.0.1460247 PMID: 7561636
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