Histamine and tele-methylhistamine in cat plasma after intravenous injection of histamine.
The effects of increased plasma histamine (Hi) on plasma tele-methylhistamine (MeHi) levels and the kinetics of Hi and MeHi elimination from plasma were studied in the cat. Hi (40 or 50 micrograms/kg) was injected intravenously and then Hi and MeHi were assayed by HPLC. Hi injection was followed by a significant increase in plasma MeHi levels, being maximal at 2-4 min. In most animals, maximal MeHi levels exceeded Hi itself. The half-lives (t1/2) of injected Hi were 0.6 and 13.3 min (mean values) in the alpha- and beta-phases, while the corresponding values for MeHi were 1.1 and 15.4 min. The t1/2 of exogenous MeHi (64 micrograms/kg, i.v.) was in the same range. Inhibitors of histamine-N-methyltransferase diminished the elimination rate of both amines studied. Plasma MeHi can thus serve as a marker for increased plasma Hi in the cat particularly because of its noticeable and delayed elevation after the rise in Hi itself.
Department of Pharmacology, Medical Faculty, University of Ljubljana, Slovenia.
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Irman-Florjanc
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Erjavec
D000818:Animals; D002415:Cats; D002851:Chromatography, High Pressure Liquid; D005260:Female; D006207:Half-Life; D006632:Histamine / Q000008:administration & dosage / Q000097:blood* / Q000494:pharmacology; D006637:Histamine N-Methyltransferase / Q000037:antagonists & inhibitors; D007275:Injections, Intravenous; D008297:Male; D008761:Methylhistamines / Q000097:blood*
D008761:Methylhistamines; D006632:Histamine; D006637:Histamine N-Methyltransferase; C020404:tele-methylhistamine