EPINEPHRINE AND NOREPINEPHRINE

The chromaffin cells of the adrenal medulla may be considered to be modified sympathetic neurons that are able to synthesize E from NE by /V-methylation. In this case the amine is Hberated into the circulation, where it exerts effects similar to those of NE in addition, E exhibits effects different from those of NE, such as relaxation of lung muscle (hence its use in asthma). Small amounts of E are also found in the central nervous system, particularly in the brain stem where it may be involved in blood pressure regulation. DA, the precursor of NE, has biological activity in peripheral tissues such as the kidney, and serves as a neurotransmitter in several important pathways in the brain (1,2). 

CA name (R)-(-)-4-[l-hydroxy-2-(methylamino)eth5l]-1,2-benze nediol (R)-(-)-4-(2-amino-1-hydroxyethyl)-1,2-benzenediol 

Data given in Specifications and Criteriafior Biochemical Compounds, Supplement Biogenicy mines and Belated Compounds. Courtesy ofithe Nationalyicademj ofiSciences. 

Kirk-Othmer Encyclopedia of Chemical Technology (4th Edition) 

Stability. E is sensitive to ait, light, heat, and alkalies. Metals, notably copper, iron, and 2inc, destroy its activity. In solution with sulfite or bisulfite, it slowly forms an inactive sulfonate (17). The red color that forms when neutral or alkaline solutions are exposed to air is caused by adrenochrome. 

IUPAC name (-)-3,4-dihydroxy-OC- [(methylamino)methyf benzyl alcohol (-)-a(aminomethyl)-3,4- dihydroxybenzyl alcohol 

Some of the physical properties of E and NE are summarized in Table 1. Table 1. Physical Properties of Epinephrine and Norepinephrine  

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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. 

Amino acid-derived hormones include the catecholamines, epinephrine and norepinephrine (qv), and the thyroid hormones, thyroxine and triiodothyronine (see Thyroid AND ANTITHYROID PREPARATIONS). Catecholamines are synthesized from the amino acid tyrosine by a series of enzymatic reactions that include hydroxylations, decarboxylations, and methylations. Thyroid hormones also are derived from tyrosine iodination of the tyrosine residues on a large protein backbone results in the production of active hormone. 

Catecholamines. The catecholamines, epinephrine (EPl adrenaline) (85), norepinephrine (NE noradrenaline) (86) (see Epinephrine and norepinephrine), and dopamine (DA) (2), are produced from tyrosine by the sequential formation of L-dopa, DA, NE, and finally EPl. EPl and NE produce their physiological effects via CC- and -adrenoceptors, a-Adrenoceptors can be further divided into CC - and a2-subtypes which in turn are divided... 

The modern usage of P2" go Asts for the treatment of asthma dates to 1903 when the effect of injected epinephrine [51-43-4] (adrenaline) C2H23NO2, (1 R = CH3) was investigated (see Epinephrine and norepinephrine) (33). As in some other modem treatments, eg, xanthines and anticholinergics, the roots of P2" go Ast therapy for asthma can be found in historical records which document the use of herbal extracts containing ephedrine [299-42-3] C qH NO, (2) as bronchodilators. Epinephrine and ephedrine are stmcturaHy related to the catecholamine norepinephrine [51-41-2] CgH NO, (1, R = H), a neurotransmitter of the adrenergic nervous system (see Neuroregulators). 

Compounds stmcturaHy related to the endogenous sympathomimetic amines epinephrine and norepinephrine have classically been employed as appetite suppressants. These agents, of which amphetamine [300-62-9], is the prototypical example, generally retain the phenethyl amine, but lack... 

The vesicular monoamine transporters (VMATs) were identified in a screen for genes that confer resistance to the parkinsonian neurotoxin MPP+ [2]. The resistance apparently results from sequestration of the toxin inside vesicles, away from its primary site of action in mitochondria. In addition to recognizing MPP+, the transporter s mediate the uptake of dopamine, ser otonin, epinephrine, and norepinephrine by neurons and endocrine cells. Structurally, the VMATs show no relationship to plasma membrane monoamine transporters. 

N euro transmitters are chemical substances called neurohormones. These are released at Hie nerve ending that facilitate the transmission of nerve impulses. The two neurohormones (neurotransmitters) of the sympathetic nervous system are epinephrine and norepinephrine Epinephrine is secreted by the adrenal medulla Norepinephrine is secreted mainly at nerve ending of sympathetic (also called adrenergic) nerve fibers (Pig. 22-2). 

Adrenergic dru mimic the activity of the sympathetic nervous system. These dragp also are called sympathomimetic druc s. Epinephrine and norepinephrine are neurohormones produced naturally by the body. Synthetic preparations of these two neurohormones,... 

The adrenergic dragp are important in the care and treatment of patients in shock. Shock is defined as a life-threatening condition of inadequate perfusion. In shock, there is an inadequate supply of arterial blood flow and oxygen delivery to the cells and tissues. The body initiates compensatory mechanisms to counteract the symptoms of shock (eg, the release of epinephrine and norepinephrine), hi some situations, the body is able to compensate and blood pressure is maintained. However, if shock is untreated and compensatory mechanisms of the body fail, irreversible shock occurs and... 

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