histamiiniH2reseptori

The histamiiniH2reseptori, also known as the histamine H2 receptor, is a cell surface receptor that is primarily activated by histamine. It belongs to the G protein-coupled receptor superfamily. Upon activation by histamine, the H2 receptor triggers a cascade of intracellular events mediated by the Gs protein. This leads to an increase in intracellular cyclic AMP (cAMP) levels.

In the stomach, H2 receptors are predominantly found on parietal cells. Activation of these receptors by histamine is a key signal for the stimulation of gastric acid secretion. Histamine is released from enterochromaffin-like (ECL) cells in the stomach, which are in turn stimulated by other hormones and neurotransmitters.

Beyond the stomach, H2 receptors are also present in other tissues, including the heart, smooth muscle, and immune cells. In the heart, their activation can lead to a positive chronotropic and inotropic effect, increasing heart rate and contractility. In the immune system, histamine acting through H2 receptors can have generally inhibitory effects on immune responses, such as mast cell degranulation and T-cell proliferation.

Drugs that block the histamine H2 receptor, known as H2 receptor antagonists or H2 blockers, are widely used to reduce gastric acid production. This makes them effective treatments for conditions like peptic ulcers, gastroesophageal reflux disease (GERD), and Zollinger-Ellison syndrome. Examples of such drugs include cimetidine, ranitidine, and famotidine.