Immunohistochemical Localization of Histamine N-Methyltransferase in Guinea Pig Tissues

Abstract

Histamine plays important roles in gastric acid secretion, inflammation, and allergic response. Histamine N-methyltransferase (HMT; EC 2.1.1.8) is crucial to the inactivation of histamine in tissues. In this study we investigated the immunohistochemical localization of this enzyme in guinea pig tissues using a rabbit polyclonal antibody against bovine HMT. The specificity of the antibody for guinea pig HMT was confirmed by Western blotting and the lack of any staining using antiserum preabsorbed with purified HMT. There was strong HMT-like immunoreactivity (HMT-LI) in the epithelial cells in the gastrointestinal tract, especially in the gastric body, duodenum, and jejunum. The columnar epithelium in the gallbladder was also strongly positive. Almost all the myenteric plexus from the stomach to the colon was stained whereas the submucous plexus was not. Other strongly immunoreactive cells included the ciliated cells in the trachea and the transitional epithelium of the bladder. Intermediately immunoreactive cells included islets of Langerhans, epidermal cells of the skin, alveolar cells in the lung, urinary tubules in the kidney, and epithelium of semiferous tubules. HMT-LI was present in specific structures in the guinea pig tissues. The widespread distribution of HMT-LI suggests that histamine has several roles in different tissues.

Guinea Pig Histamine N-Methyltransferase: cDNA Cloning and mRNA Distribution

“…3C). Using a rabbit polyclonal antibody against purified bovine HMT, Tahara et al (15) showed strong immunoreactivity in almost the same localization as that in the present study, suggesting that HMT has a crucial role in the jejunum. In guinea pig stomach, lung and spleen, the 1.6-kb transcript was also observed (Fig.…”

4. Synthesis, metabolism and release of histamine

“…Conversely, HNMT is a cytosolic enzyme that is responsible for inactivation of intracellular histamine [1]. Analysis of the cellular localisation of HNMT in guinea-pig tissues, using immunohistochemical staining, revealed a widespread and diverse distribution of the enzyme [8]. Currently no information is available regarding the cell-specific expression of HNMT in porcine and human tissues.…”

Release and permeation of histamine in isolated caecum epithelia of pigs

“…Part of the permeation pathway, however, can be assumed to be transcellular. This can be concluded from the facts that a) catabolism, at least by HMT, is essentially localized within gastrointestinal epithelial cells [35,36] and that b) the sm fl uxes of hist-rad (Fig. 3) or histamine (see results: "Epithelial permeation of exogenous histamine") exceeded their corresponding ms fl uxes.…”