Measurement of T-kinin in rat plasma using a specific radioimmunoassay

Finbarr O'Harte, D. David Smith, Stephen J. Lanspa, J. Michael Conlon

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6 Citations (Scopus)

Abstract

T-kinin (Ile-Ser-Bradykinin) has been isolated only from the plasma of the rat and it is unclear whether the peptide, or its biosynthetic precursor, T-kininogen, circulates in the human. An NH2-terminally directed antiserum to T-kinin was raised in rabbits using an immunogen prepared by coupling the free-SH group of T-kinin extended from its COOH-terminus by a cysteinyl residue to an -NH2 group on human serum albumin. A radioimmunoassay was developed using this antiserum and 125I-labelled [Tyr10]T-kinin as tracer that was sensitive (least-detectable concentration 3 fmol/tube) and relatively specific for T-kinin (cross-reactivity with bradykinin and kallidin < 1%). Treatment of rat plasma with an excess of trypsin in the presence of a kininase inhibitor generated T-kinin immunoreactivity equivalent to 455 ± 71 pmol/ml (mean ± S.E.M.; n = 9) and this immunoreactivity was eluted from a reversed-phase HPLC column as a single peak with the same retention time as synthetic T-kinin. In contrast, treatment of plasma from healthy human subjects (n = 8) and from patients (n = 8) with inflammation due to acute or chronic gastrointestinal disease under the same conditions did not generate any detectable T-kinin immunoreactivity. It is concluded, therefore, that T-kininogen, the biosynthetic precursor of T-kinin in the rat, is either absent from the plasma of human subjects or is present in a concentration < 30 fmol/ml. Similarly, T-kininogen is probably not an acute phase reactant in humans.

Original languageEnglish
Pages (from-to)139-148
Number of pages10
JournalRegulatory Peptides
Volume41
Issue number2
DOIs
Publication statusPublished - 22 Sep 1992

Keywords

  • Acute phase reactant
  • Bradykinin
  • Kininogen
  • Rat plasma
  • T-kinin

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