Histamine physiological roles

Histamine in the Cardiovascular System. It has been known for many years that histamine is present in sympathetic nerves and has a distribution within the heart that parallels that of norepinephrine (see Epinephrine and norepinephrine). A physiological role for cardiac histamine as a modulator of sympathetic responses is highly plausible (15). A pool of histamine in rat heart located neither in mast cells nor in sympathetic nerves has been demonstrated. The turnover of this metaboHcaHy active pool of histamine appears to be maintained by normal sympathetic activity. 

Histamine in the nervous system may participate in a variety of brain functions. Several of the suspected physiological roles for histamine are related to its ability to increase the neuronal excitability [1, 2,15]. For example, mutant mice lacking the H, receptor show defective locomotor and exploratory behaviors [57], Neuronal histamine may increase attention and/or arousal by many mechanisms, including by enhancing sensory input [58], All available evidence from several species shows that histaminergic neurons, when activated, increase wakefulness... 

Sakata, T., Kurokawa, M., Oohara, A. and Yoshimatsu, H. A physiological role of brain histamine during energy deficiency. Brain Res. Bull 35 135-139,1994. 

Knowledge of the physiological role of histamine in the CNS and evidence for the existence of discrete neuronal networks that could be called histaminergic are still evolving. Histamine-mediated hypothermia, emesis, and hypertension have been shown to exist, and the well-known sedative effects of Hj antihistamines are centrally mediated. 

Histamine was synthesized in 1907 and later isolated from mammalian tissues. Early hypotheses concerning the possible physiologic roles of tissue histamine were based on similarities between the effects of intravenously administered histamine and the symptoms of anaphylactic shock and tissue injury. Marked species variation is observed, but in humans histamine is an important mediator of immediate allergic (such as urticaria) and inflammatory reactions, although it plays only a modest role in anaphylaxis. Histamine plays an important role in gastric acid secretion (see Chapter 62) and functions as a neurotransmitter and neuromodulator (see Chapters 6 and 21). Newer evidence indicates that histamine also plays a role in chemotaxis of white blood cells. 

Histamine in the Cardiovascular System. Histamine is present in sympathetic nerves and has a distribution wilhin the heart that parallels that or norepinephrine. A physiological role fur cardiac histamine as a modulator of sympathetic responses is highly plausible. 

Bado, A., Dubrasquet, M., Lewin, M.J.M., 1990. Evidence of histamine H3 receptors in the stomach physiological role in gastric acid regulation. Gastroenterology 98 (Suppl), A17. 

Histamine was synthesized in 1907 and later isolated from mammalian tissues. Early hypotheses concerning the possible physiologic roles of tissue histamine were based on similarities between histamine s actions and the symptoms of anaphylactic shock and tissue injury. Marked species variation is observed, but in humans histamine is an important mediator of immediate allergic and... 

Of their many preformed intracellular mediators, histamine, not only plays an important physiological role, but can be used as a marker for these cells. In the human peripheral blood, the basophil is the only leukocyte that contains histamine. As a result, histamine release from human blood leukocyte preparations can be used to monitor basophil degranulation. In this chapter we will describe the histamine release assay, alternative techniques to measure the concentration of histamine and, finally, a method to purify human basophils to confirm that the chemokines are acting directly on the basophil. 

No Heparin Heparin normally occurs as a macromolecule complexed with histamine in mast cells where its physiologic role is unknown. It is extracted for commercial use from porcine intestine or bovine lung. Heparin is a mixture of straight-chain anionic glycosaminoglycans... 

Beaven, M.A. (1978). Histamine its role in physiological and pathological processes. Monogr. Allergy 13, 1-10. 

Histamine released from mast cells plays an important physiological role in immediate hypersensitivity and allergic responses. In addition, histamine functions as a neurotransmitter in the CNS and it is a potent stimulus for gastric acid secretion. These actions depend on the interaction of histamine with two types of receptors, Hi and H2. Hi and H2 receptors are coupled via G proteins to phospholipase C and adenylyl cyclase, respectively. The principal H3 receptor response is stimulation of gastric acid secretion, whereas other actions of histamine (e.g., smooth muscle contraction, vasodilation, increased capillary permeability, pain, and itching) are prunarily mediated by Hi receptors. 

In Chapter 1, the structure, synthesis and toxicity of ricin, a protein present in the endosperm cells of the seeds of the castor oil plant, are described and possible uses of this toxic agent in immunology as conjugates with antibodies are discussed. The biochemical and pharmacological evidence for the presence of functional histamine receptors in the mammalian central nervous system is set out in Chapter 2. Chapter 3 covers the chemical properties of molybdenum-containing enzymes such as aldehyde oxidase and xanthine oxidase, although their physiological roles are by no means clear. 

Histamine, produced in many tissues, is s)mthesized by removing the carboxyl group from the amino acid histidine (Figure 16.8). It has many, often anno)dng, physiological roles. Histamine is released during the allergic response. It causes the itchy skin rash associated with poison ivy or insect bites. It also promotes the red, watery eyes and respiratory s)tmptoms of hay fever. 

Autacoids are endogenous molecules with powerful pharmacologic effects but poorly defined physiologic roles. Histamine and serotonin (5-hydroxytryptamine 5-HT) are two of the most important autacoids. Both are synthesized in the body from amino acid precursors and then eliminated by amine oxidation the pathways of synthesis and metabolism are very similar to those used for catecholamine synthesis and metabolism. The ergot alkaloids are a heterogeneous group of drugs that interact with serotonin receptors, dopamine receptors, and alpha receptors. They are included in this chapter because of their effects on serotonin receptors and on smooth muscle. 

Histamine is formed from the amino acid histidine and is stored in high concentrations in vesicles in mast cells. Histamine is metabolized by the enzymes monoamine oxidase and diamine oxidase. Excess production of histamine in the body (by. for example, systemic mastocytosis) can be detected by measurement of imidazoleacetic acid (its major metabolite) in tbe urine. Because it is released from mast cells in response to IgE-mediated (immediate) allergic reactions, this autacoid plays an important pathophysiologic role in seasonal rhinitis (hay fever), urticaria, and angioneurotic e ma. Histamine also plays an important physiologic role in the control of acid secretion in the stomach and as a neurotransmitter. 

Physiology is the study of function. The classical procedure used to define physiological roles is by extirpation, ablation or nerve section to reveal inadequate or inappropriate function in the absence of the postulated mechanism. This approach cannot be used to study the physiological role of arachidonate metabolites since they are not organ-localized like the adrenal steroids or concentrated in specific cells like the adrenergic transmitters. The problem is compounded also by the fact that arachidonate oxygenation is almost a universal phenomenon. Finally the metabolites are not stored like histamine or serotonin but are released immediately upon synthesis. Consequently it is always necessary to initiate synthesis to study release. Thus release is synonymous with synthesis. 

Thus, although histamine may play a physiological role in cardiovascular health, excess histamine, a result of physical or emotional stress or a chronic disease/inflammatory state, appears to elicit atherogenic effects. In fact, inhibition of histamine synthesis in experimental diabetes reduced aortic albumin accumulation in experimental diabetes, lessening the disease complications (Hollis et al, 1983). 

Gross, S. S., Guo, Z. G., Levi, R., Bailey, W. H., and Chenouda, A. A., 1984, Release of histamine by sympathetic nerve stimulation in the guinea pig heart and modulation of adrenergic responses—a physiological role for cardiac histamine Circ. Res. 54 516-526. 

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