Determination of Histidine Decarboxylase Activity

Summary . Histamine catabolism in vivo was studied in mice subjected to various forms of pretreatment; tissues from mice killed 2·5 min after intravenous injection of 14C‐histamine were assayed for 14C‐histamine, 14C‐methylhistamine and total 14C. . Pretreatment of mice with aminoguanidine, an inhibitor of diamine oxidase, strongly increased levels of 14C‐histamine in intestine; pretreatment with aminoguanidine plus a monoamine oxidase inhibitor strongly increased levels of 14C‐methylhistamine in liver. Effects in other tissues are reported and discussed. . Pretreatment of mice with non‐isotopic methylhistamine increased levels of 14C‐histamine in liver. Methylhistamine is the first known inhibitor of histamine‐methylation in vivo. . Pretreatment of mice with inhibitors of protein synthesis, drugs which reduce the basal activity of histidine decarboxylase and which block its activation, failed to affect histamine catabolism. . Pretreatment of mice with endotoxin or with Freund's adjuvant, irritants known to cause activation of histidine decarboxylase, failed to affect histamine catabolism. . There was no evidence of parallelism between the histamine‐destroying enzymes and the histamine‐forming enzyme, histidine decarboxylase, either in distribution or ability to undergo changes in activity. No support was obtained for the view that histamine‐catabolizing enzymes play a role in the local control of responses to newly formed histamine.

Section: Methodsmentioning

confidence: 99%

In vivo studies on histamine catabolism and its inhibition

Reilly

Schayer

1970

“…In the atria, total radioactivity was measured in the perchloric acid extract. The (14C] -histamine assay was carried out according to the isotope dilution method of Schayer (1968). The [14C1 -methyl-histamine was assayed by the method of Snyder, Axelrod & Bauer (1964).…”

Section: Extraction and Analysesmentioning

confidence: 99%

INTERACTION OF HISTAMINE H₁‐ AND H₂‐RECEPTOR ANTAGONISTS WITH HISTAMINE UPTAKE AND METABOLISM BY GUINEA‐PIG ISOLATED ATRIUM AND MOUSE NEOPLASTIC MAST CELLS in vitro

Fantozzi

Franconi

Mannaioni

et al. 1975

1Burimamide, metiamide, chlorpheniramine, triprolidine and cocaine, were tested as inhibitors of histamine uptake and metabolism in the guinea-pig atrium and in mouse neoplastic mast cells. 2 Cocaine did not affect the uptake and metabolism of histamine, either in the atrium or in the mast cells. All the antihistamines tested blocked the uptake and metabolism of histamine in both preparations. The order of potency was burimamide > chlorpheniramine > triprolidine > metiamide in the atrium; and burimamide > metiamide > triprolidine > chlorpheniramine, in the mast cells. 3 Comparison of the present results with the antihistamine activity of these blocking agents suggests that no correlation exists between the receptor blocking activity and the ability of these substances to act as inhibitors of histamine uptake and metabolism.

“…The ["4C]-histamine assay was carried out according to the isotope dilution (BSH) method of Schayer (1968).…”

Section: Extraction and Analysismentioning

confidence: 99%

Uptake, disposition and metabolism of histamine in isolated heart preparations

Mannaioni

Moroni

1973

Summary1. The uptake and metabolism of histamine by the guinea-pig heart and by the isolated electrically driven guinea-pig left atria was studied with both labelled and unlabelled histamine. 2. Histamine uptake took place against a concentration gradient and, at low concentrations, this was blocked by hypoxia plus glucose deprivation or by a toxic dose of ouabain. 3. The histamine taken up was retained by cardiac tissues and mainly metabolized into methyl-histamine and other metabolites. The uptake and metabolism of histamine was higher in atria than in ventricles thus reflecting the regional distribution of endogenous histamine and mast cell numbers. 4. The uptake and metabolism of histamine were greatly reduced in hearts which had been depleted of mast cells, by combining cardiac anaphylaxis and (+)-tubocurarine (1 mg/ml), but pretreatment of guinea-pigs with 6-hydroxydopamine failed to affect uptake of total radioactivity in the isolated left atria. 5. In the guinea-pig heart histamine appears to be taken up, stored and metabolized in at least two pools, one of which is linked to the mast cells.