Measurement of T-kinin in rat plasma using a specific radioimmunoassay.
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 less than 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 less than 30 fmol/ml. Similarly, T-kininogen is probably not an acute phase reactant in humans.
O'Harte
F
F
Department of Biomedical Sciences, Creighton University Medical School, Omaha, NE 68178.
Smith
D D
DD
Lanspa
S J
SJ
Conlon
J M
JM
D000328:Adult; D000595:Amino Acid Sequence; D000818:Animals; D001920:Bradykinin / Q000031:analogs & derivatives* / Q000097:blood / Q000737:chemistry; D005260:Female; D005759:Gastroenteritis / Q000097:blood; D006801:Humans; D007704:Kininogens / Q000097:blood; D008297:Male; D008969:Molecular Sequence Data; D011863:Radioimmunoassay / Q000379:methods*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013045:Species Specificity
D007704:Kininogens; C039065:T-kinin; D001920:Bradykinin