title: An improved method for the determination of islet amyloid polypeptide levels in plasma.
abstract: We describe an improved method for the determination of islet amyloid polypeptide (IAPP) levels in plasma. Plasma is first extracted with acid-acetone, followed by a specific and sensitive radioimmunoassay (RIA) for IAPP using rabbit-anti-human-IAPP serum. Recovery of synthetic IAPP from plasma was 82 +/- 6% (n = 16). Standard samples, prepared in 'hormone-free' serum, were also extracted with acid-acetone. Displacement curves of serially diluted acid-acetone extracted plasma samples were parallel to the standard curve. The lower detection limit of the RIA was 2.3 +/- 0.1 fmol/sample (n = 5). Intra-assay variations for IAPP concentrations of 4, 17 and 32 pM were 16.3% (n = 10), 9.2% (n = 10) and 6.2% (n = 10); interassay variations were 35.9% (n = 14), 19.9% (n = 15) and 15.4% (n = 15), respectively. Non-stimulated IAPP levels ranged from 2.4 to 12 pM (mean 6 +/- 4 pM, n = 10) in healthy control subjects. IAPP was not detectable in type 1 (insulin-dependent) diabetic patients before and after glucagon administration. In type 2 (non-insulin-dependent) diabetic patients basal levels ranged from 2.2 to 14.5 pM and glucagon-stimulated levels ranged from 2.2 to 38.9 pM. The increase in IAPP varied from 0 to 24.4 pM. The anti-human-IAPP serum had full cross-reactivity with rat IAPP (= mouse IAPP). Transgenic mice overexpressing the human IAPP gene showed elevated plasma IAPP levels as compared to (non-transgenic) control mice. It is concluded that the method presented for the determination of IAPP in plasma is reliable and easy to perform, yielding reproducible results.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Internal Medicine, Academic Hospital, Utrecht, The Netherlands.
authors.forename: K L
authors.initials: KL
authors.lastname: van Hulst
authors.forename: W H
authors.initials: WH
authors.lastname: Hackeng
authors.forename: J W
authors.initials: JW
authors.lastname: Höppener
authors.forename: B C
authors.initials: BC
authors.lastname: van Jaarsveld
authors.forename: M G
authors.initials: MG
authors.lastname: Nieuwenhuis
authors.forename: M A
authors.initials: MA
authors.lastname: Blankenstein
authors.forename: C J
authors.initials: CJ
authors.lastname: Lips
mesh_terms: D000682:Amyloid / Q000097:blood*; D002096:C-Peptide / Q000097:blood; D003429:Cross Reactions; D003922:Diabetes Mellitus, Type 1 / Q000097:blood; D005934:Glucagon / Q000494:pharmacology; D006801:Humans; D007275:Injections, Intravenous; D058228:Islet Amyloid Polypeptide; D007515:Islets of Langerhans / Q000187:drug effects; D011863:Radioimmunoassay
chemical_list: D000682:Amyloid; D002096:C-Peptide; D058228:Islet Amyloid Polypeptide; D005934:Glucagon