Insulin receptors in Xenopus laevis liver and forelimb regenerates and the effects of local insulin deprivation on regeneration

Bryce J. Cowan, Ramsey Foty, Richard A. Liversage

Research output: Contribution to journalArticle

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Abstract

As forelimb regeneration in Xenopus laevis is mainly a cell proliferative event which results in a spike‐shaped appendage, we set out to examine the possibility that insulin is a growth‐promoting factor in this process. The objectives were 1) to detect the presence of insulin receptors (IRs) in the liver (a specific target organ for insulin) and IRs in the forelimb regenerates of X. laevis, 2) to determine whether the receptor is similar to IRs identified in other organisms, and 3) to absorb insulin locally by implanting anti‐insulin antibody‐soaked hydrolyzed polyacrylamide beads into regenerating forelimb outgrowths in order to assess the effects of insulin deprivation on regeneration. The results show that IRs are present in Xenopus liver plasma membranes (XLPM) as well as in plasma membranes of 21 day forelimb regenerates. Insulin binding to this receptor is time‐dependent and specific, as unlabeled bovine insulin competes with radioiodinated insulin for binding to XLPM more effectively than insulin‐like growth factor‐I, guinea pig insulin, or glucagon. Scatchard analysis of insulin binding to XLPM describes a two binding site receptor possessing a low affinity (0.16 nM−1), high capacity (3.2 ± 0.9 pM/mg) binding site and a high affinity (2.7 nM−1), low capacity (0.5 ± 0.3 pM/mg) binding site. The holoreceptor has a molecular mass of 380 kDa. The reduced receptor has subunits of 130 kDa and 95 kDa. The 95 kDa subunit undergoes autophosphorylation following insulin stimulation. Implantation of hydrolyzed poly‐acrylamide beads, saturated with anti‐insulin antibody, into regenerating Xenopus Forelimbs significantly impeded development of the regenerates and, therefore, demonstrates that insulin is required for growth of Xenopus forelimb regenerates. © 1995 Wiley‐Liss, Inc.

Original languageEnglish (US)
Pages (from-to)130-141
Number of pages12
JournalJournal of Experimental Zoology
Volume273
Issue number2
DOIs
StatePublished - Jan 1 1995

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Xenopus laevis
forelimbs
insulin
liver
Xenopus
plasma membrane
binding sites
receptors
polyacrylamide
insulin receptors
protein phosphorylation
glucagon
appendages
guinea pigs
molecular weight

All Science Journal Classification (ASJC) codes

  • Animal Science and Zoology

Cite this

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abstract = "As forelimb regeneration in Xenopus laevis is mainly a cell proliferative event which results in a spike‐shaped appendage, we set out to examine the possibility that insulin is a growth‐promoting factor in this process. The objectives were 1) to detect the presence of insulin receptors (IRs) in the liver (a specific target organ for insulin) and IRs in the forelimb regenerates of X. laevis, 2) to determine whether the receptor is similar to IRs identified in other organisms, and 3) to absorb insulin locally by implanting anti‐insulin antibody‐soaked hydrolyzed polyacrylamide beads into regenerating forelimb outgrowths in order to assess the effects of insulin deprivation on regeneration. The results show that IRs are present in Xenopus liver plasma membranes (XLPM) as well as in plasma membranes of 21 day forelimb regenerates. Insulin binding to this receptor is time‐dependent and specific, as unlabeled bovine insulin competes with radioiodinated insulin for binding to XLPM more effectively than insulin‐like growth factor‐I, guinea pig insulin, or glucagon. Scatchard analysis of insulin binding to XLPM describes a two binding site receptor possessing a low affinity (0.16 nM−1), high capacity (3.2 ± 0.9 pM/mg) binding site and a high affinity (2.7 nM−1), low capacity (0.5 ± 0.3 pM/mg) binding site. The holoreceptor has a molecular mass of 380 kDa. The reduced receptor has subunits of 130 kDa and 95 kDa. The 95 kDa subunit undergoes autophosphorylation following insulin stimulation. Implantation of hydrolyzed poly‐acrylamide beads, saturated with anti‐insulin antibody, into regenerating Xenopus Forelimbs significantly impeded development of the regenerates and, therefore, demonstrates that insulin is required for growth of Xenopus forelimb regenerates. {\circledC} 1995 Wiley‐Liss, Inc.",
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Insulin receptors in Xenopus laevis liver and forelimb regenerates and the effects of local insulin deprivation on regeneration. / Cowan, Bryce J.; Foty, Ramsey; Liversage, Richard A.

In: Journal of Experimental Zoology, Vol. 273, No. 2, 01.01.1995, p. 130-141.

Research output: Contribution to journalArticle

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