KINETICS OF HISTAMINE AND TELE-METHYLHISTAMINE ELIMINATION FROM RAT PLASMA

Plasma levels of histamine (Hi) and tele-methylhistamine (MeHi) were measured by HPLC after intravenous bolus injection of Hi (45 mug/kg) or MeHi (55 mug/kg) in the rat. Increases in plasma Hi (from baseline 2.8 +/- 0.4 to about 50 ng/ml at 2 min after the injection) were accompanied by a significant increase in MeHi levels (baseline 1.2 +/- 0.3 ng/ml rising up to 11 ng/ml, 6 min after Hi application). After rapid intravenous injection, Hi and MeHi elimination from plasma could be fitted by a double exponential function with half lives in the alpha and beta phases of about 20 sec and 4 min (Hi) or 1 min and 43 min (MeHi). The results suggest that measurement of plasma MeHi, as an indirect marker of Hi release, has an advantage over measuring Hi itself.