Histamine Aspects in Acid Peptic Diseases and Cell Proliferation

Abstract

Histamine is a naturally occurring imidazole derivative. In human, histamine is present in nearly all tissues of the body. Four different histamine receptors subtypes have been cloned and designated as H1 to H4 receptors. H1 and H2 receptors have wide distribution in comparison to H3 and H4 receptors. H1 antihistamines (H1 receptor blockers) are among the most widely used drugs. H2 receptor activation is a strong stimulant for gastric acid secretion. Hence, histamine H2 receptors (H2R) antagonist has been used for the treatment of peptic ulcer and other gastric hypersecretory states such as Zollinger-Ellison syndrome. The H3 receptors have also been cloned and their receptor ligands are in early clinical phase trials for obesity and other disorders like memory, learning deficit and epilepsy. The most recently discovered H4 receptor antagonists are being investigated for their use in inflammatory conditions such as asthma and rheumatoid diseases. Histamine is also involved in other functions, such as the cell proliferation and differentiation. Therefore its role is also defined in embryogenesis, organogenesis and tumorigenesis. In this chapter, we review H2 receptor antagonist, their present status in acid-peptic diseases and the emerging role of histamine in cell proliferation and differentiation with special reference to tumorigenesis.