Evidence for separate receptors for insulin and insulin-like growth factor-I in choroid plexus of rat brain by quantitative autoradiography

D. A. Davidson, N. J. Bohannon, E. S. Corp, D. P. Lattemann, S. C. Woods, D. Porte, D. M. Dorsa, D. G. Baskin

Research output: Contribution to journalArticle

26 Scopus citations

Abstract

Binding of insulin and insulin-like growth factor-I (IGF-I) to the choroid plexus was quantitatively characterized using autoradiography and computer densitometry. Slide-mounted brain slices were incubated in 0.1 nM [125I]-insulin or [125I]-[Thr59]IGF-I. To determine specificity of the binding sites, the labeled peptides were mixed with unlabeled analogues. Autoradiography was done with LKB Ultrofilm and analyzed with a computer image analysis system and program for densitometry. Results showed that binding was time and temperature dependent and reversible. Binding of the iodinated insulin and IGF-I was inhibited by unlabeled peptides in a dose-dependent manner. The rank order of potency of these peptides in competing for the choroid plexus iodoinsulin binding sites was: chicken insulin > porcine insulin > desoctapeptide insulin > IGF-I. IGF-I was more potent than porcine insulin in competing for the choroid plexus iodolGF-I binding sites. somatostatin was ineffective. Non-linear regression analysis revealed the presence of high- (K(d) 1.3 ± 0.2 nM) and low-affinity (K(d) 36 ± 1.4 nM) binding sites for insulin and a single high-affinity binding site (K(d) 3.1 ± 0.3 nM) for IGF-I in the choroid plexus. There were approximately 50 times more binding sites (B(max)) for IGF-I than for insulin high-affinity sites, whereas the number of low-affinity sites for insulin was about equal to the number of IGF-I high-affinity sites. The results of these binding studies with iodinated insulin and [Thr59]IGF-I support the conclusion that the rat choroid plexus has separate high-affinity receptors for insulin and IGF-I, and that the IGF-I receptors outnumber the insulin receptors.

Original languageEnglish (US)
Pages (from-to)1289-1294
Number of pages6
JournalJournal of Histochemistry and Cytochemistry
Volume38
Issue number9
DOIs
StatePublished - 1990

Keywords

  • brain
  • choroid plexus
  • insulin
  • insulin-like growth factor-I
  • quantitative autoradiography
  • rat
  • receptors

ASJC Scopus subject areas

  • Anatomy
  • Histology

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