Methylhistamine in guinea pig brain

Measurement of tele-methylhistamine and histamine in human cerebrospinal fluid, urine, and plasma

A gas chromatographic-mass spectrometric method described by us to measure tele-methylhistamine (t-MH) in brain was used to measure t-MH in human cerebrospinal fluid (CSF), urine and plasma. The presence of t-MH in these body fluids was rigorously established. No pros-methyl-histamine could be detected, and it was used as internal standard to quantify t-MH in the fluids. The mean levels of t-MH were: urine, 943 pmol/mg creatinine; plasma, 12.3 pmol/ml; and CSF, 2.2 pmol/ml. Parallel measurements of histamine by a radioenzymatic method showed, respectively, 182 pmol/mg creatinine; 19.5 pmol/ml; and 388 pmol/ml. The levels of HA in CSF, much higher than those of its metabolite, t-MH, are high enough to stimulate HA receptors in the central nervous system.

Histamine and some of its metabolites in human body fluids

The concentrations of histamine, t-methylhistamine and t-methylimidazoleacetic acid were measured in human cerebrospinal fluid, plasma and urine, Especially noteworthy are the levels of histamine in cerebrospinal fluid which are far higher than those of t-methylhistamine and of t-methylimidazoleacetic acid, and high enough to stimulate histamine receptors in the central nervous system. It is suggested that mast cells, which surround the subarachnoid space, may contribute histamine to the cerebrospinal fluid and may offer a target for drugs and for immunologic actions. The t-methylhistamine and t-methylimidazoleacetic acid levels in cerebrospinal fluid may reflect central histaminergic activity, although a source of these metabolites in addition to histamine needs to be considered.

Ontogeny of subcellular distribution of rat brain tele-methylhistamine

The whole brain content and subcellular distribution of histamine and its metabolite, tele-methylhistamine, were studied during postnatal development of the rat. Brain methylhistamine levels were similar to or greater than histamine levels, indicating that histamine methylation is a major metabolic pathway in neonatal brain, as it is in adults. When calculated per brain, histamine, methylhistamine, and histamine methyltransferase were all maximal 10 days after birth. In neonates, brain histamine was found almost entirely in nuclear fractions, whereas methylhistamine was found almost exclusively in supernatant fractions. By day 20, however, a greater proportion of both amines was localized in subcellular fractions containing synaptosomes, a finding consistent with histamine's suggested transmitter role. The ontogenic pattern of brain methylhistamine questions the mast cell origin of neonatal histamine, but may be consistent with a role for histamine in brain development.

Determination of N tau-methylhistamine in plasma and urine by isotope dilution mass fragmentography

The determination in N tau-methylhistamine by gas chromatography-mass spectrometry is described using bis-heptafluorobutyryl derivatives and deuterium labelled N tau-methylhistamine as internal standard. A description of the synthesis of the internal standard, N tau-trideuteromethylhistamine, is given. Normal concentrations for plasma were 1.4 +/- 0.4 microgram/l (mean +/- 1 S.D., n = 10). The normal values for urine ranged from 60 to 280 microgram/24 h (n = 20). Five asthmatic patients showed above-normal plasma concentrations.

An improved GCMS method to measure tele-methylhistamine

The presence of tele-methylhistamine (t-MH), the metabolite of histamine in rat brain, and its relationship to putative histaminergic transmission have been the subjects of recent work. We modified the GCMS method of Hough et al. (1979) to enhance both sensitivity and reproducibility. The substitution of KOH for NaOH to extract t-MH considerably improved the recovery. Evaporation of the extract in 0.2 N HCl, as used in the earlier method, reduced the formation of heptafluorobutyryl derivative; substitution with 0.01 N HCl more than doubled the recovery of the derivative. The derivatization procedure itself was changed, the new method exhibiting significantly improved reproducibility. Standard curve of t-MH obtained at different times after derivatization were indistinguishable. The modified method is capable of measuring less than 1 pmole of t-MH. The t-MH content found in nine rat brain regions agree with previously reported values.