Insulin-like growth factor-I and insulin-like growth factor-binding protein in the toad, Bufo woodhousei

Martha K. Pancak-Roessler, Phillip Lee

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

Molecular weight characteristics and plasma concentrations of insulin-like growth factor-I (IGF-I) and its binding protein (IGF-BP) were investigated in the toad, Bufo woodhousei. IGF-I and IGF-BP were measured by radioimmunoassay (RIA, Kd = 0.37 ± 0.04 ng/ml) and charcoal-separated ligand binding assay, respectively, in male toad plasma and adult male human donor plasma using a synthetic human IGF-I standard. Prior to the IGF-I RIA, samples were acid-ethanol extracted. Molecular weight characteristics were determined using size exclusion chromatography. At neutral pH (pH = 7.4), IGF-I immunoreactivity and IGF-BP eluted at molecular weight >66 kDa in both toad and human plasma. Acid chromatography (pH ∼3) resulted in the separation of IGF-I from its binding protein and consequently a shift of IGF-I immunoreactivity to the low molecular weight fractions (∼8 kDa) for both toad and human. IGF-BP activity shifted to molecular weight ∼50 kDa. Toad plasma IGF-I and IGF-BP activity exhibited differences according to season: IGF-I levels were low in the spring (March = 0.48 ± 0.11 ng eq/ml), increased progressively to reach a peak in July (5.84 ± 2.5 ng eq/ml), and decreased to low levels again in the fall (October = 0.60 ± 0.08, November = 0.45 ± 0.09 ng eq/ml). Plasma IGF-BP activity demonstrated a similar pattern (March = 17.4 ± 2.5, July = 35.0 ± 2.4, November = 12.6 ± 3.2% specific binding). IGF-I was produced for at least 72 hr when toad liver explants were cultured in serum-free medium, indicating that the liver is a source of IGF-I in anurans.

Original languageEnglish (US)
Pages (from-to)263-272
Number of pages10
JournalGeneral and Comparative Endocrinology
Volume78
Issue number2
DOIs
StatePublished - 1990
Externally publishedYes

Fingerprint

Bufonidae
Insulin-Like Growth Factor Binding Proteins
insulin-like growth factor binding proteins
Bufo
toads
insulin-like growth factor I
Insulin-Like Growth Factor I
Anura
binding proteins
Carrier Proteins
Molecular Weight
molecular weight
liver
Acids
Charcoal
Liver
acids

ASJC Scopus subject areas

  • Endocrinology

Cite this

Insulin-like growth factor-I and insulin-like growth factor-binding protein in the toad, Bufo woodhousei. / Pancak-Roessler, Martha K.; Lee, Phillip.

In: General and Comparative Endocrinology, Vol. 78, No. 2, 1990, p. 263-272.

Research output: Contribution to journalArticle

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abstract = "Molecular weight characteristics and plasma concentrations of insulin-like growth factor-I (IGF-I) and its binding protein (IGF-BP) were investigated in the toad, Bufo woodhousei. IGF-I and IGF-BP were measured by radioimmunoassay (RIA, Kd = 0.37 ± 0.04 ng/ml) and charcoal-separated ligand binding assay, respectively, in male toad plasma and adult male human donor plasma using a synthetic human IGF-I standard. Prior to the IGF-I RIA, samples were acid-ethanol extracted. Molecular weight characteristics were determined using size exclusion chromatography. At neutral pH (pH = 7.4), IGF-I immunoreactivity and IGF-BP eluted at molecular weight >66 kDa in both toad and human plasma. Acid chromatography (pH ∼3) resulted in the separation of IGF-I from its binding protein and consequently a shift of IGF-I immunoreactivity to the low molecular weight fractions (∼8 kDa) for both toad and human. IGF-BP activity shifted to molecular weight ∼50 kDa. Toad plasma IGF-I and IGF-BP activity exhibited differences according to season: IGF-I levels were low in the spring (March = 0.48 ± 0.11 ng eq/ml), increased progressively to reach a peak in July (5.84 ± 2.5 ng eq/ml), and decreased to low levels again in the fall (October = 0.60 ± 0.08, November = 0.45 ± 0.09 ng eq/ml). Plasma IGF-BP activity demonstrated a similar pattern (March = 17.4 ± 2.5, July = 35.0 ± 2.4, November = 12.6 ± 3.2{\%} specific binding). IGF-I was produced for at least 72 hr when toad liver explants were cultured in serum-free medium, indicating that the liver is a source of IGF-I in anurans.",
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