ヨードカルノシンの研究。モノヨードおよびジヨードカルノシンの平滑筋に対する作用

抄録

Carnosine was iodinated and separated into 4-monoiodocarnosine (MIC) and 2, 4-diiodocarnosine (DIC) by Sephadex G-10 column chromatography, and their effect on smooth musole was examined. Carnosine induced smooth muscle contraction, while its iodinated products, MIC and DIC, induced relaxation of the rat intestinal duodenum. This fact suggested that a hydrogen atom at position 4 in the imidazole ring of carnosine is essential for the contraction, and its substitution by iodine produced the relaxation effect. The specificity of iodocarnosine antagonism was examined in guinea-pig ileum by inhibiting contraction induced by various agonists. It was found that MIC and DIC inhibited contraction stimulated by histamine and prostaglandine F_2a(PGF_2a), but they did not inhibit acetylcholine and bradykinin. This result suggested that anti-histamine effect of iodocarnosine may be ascribable to its analogous structure to histamine molecule. Therefore, other iodinated compounds having structure similar to histamine were examined for ability to inhibit histamine-stimulated smooth muscle contraction. Anti-histamine effect of monoiodohistidine (MIH) and diiodohistidine (DIH) was considerably weaker than that of β-alanyl-MIH (MIC) and β-alanyl-DIH (DIC), and monoiodohistamine did not exert anti-histamine effect at all. This suggested that at least MIH moiety is essential for the anti-histamine activity, and β-alanyl residue may augment the activity. Iodocarnosine was capable of inhibiting the contraction due to anaphylaxis in guinea-pig ileum that had been sensitized by bovine serum albumin. The anaphylatic reaction induced the release of histamine, PG's, slow reacting substance of anaphylaxis (SRS-A), and inflammatory factors in the antigen-antibody reaction. It may be concluded that iodocarnosines (either MIC or DIC) have anti-histamine, anti-PG, and anti-inflammatory effect.