Metabolism contractile process

Proteins are biopolymers having a molecular weight arbitrarily greater than 5,000 dal tons. They are essential for functions in cellular structure, catalysis, metabolic regulation and contractile processes. They also play an important part in the defensive and protective mechanisms in animals. 

Arachidonic acid released from membrane phospholipids or other sources is metabolized by the LO pathway to the smooth muscle contractile and vasoactive leukotrienes (LT), LTC4, and LTD4, as well as to the potent chemoattractant LTB4. These molecules are intimately involved in inflammation, asthma, and allergy, as well as in other multiple physiological and pathological processes. For example, cirsiliol (3, 4, 5-trihydroxy-6,7-dimethoxyflavone) proved to be a potent inhibitor of 5-LO (IC50, 0.1 pM) derived from basophilic leukemia cells and peritoneal polymorphonuclear leukocytes. 

The toxicity of papaverine has been studied,36 as have its effects on energy processes in myocardial mitochondria,37 on the release and metabolism of dopamine,38 on contractile force and C-nucleotide levels in dog myocardium,39 on serum-induced spasms in cerebral arterioles,40 and on production of PGE2 by rabbit gastric mucosa,41 and the biological effects of drotaverine,42 N-benzoylpapaverinium chloride,43 and norlaudanosoline44 have been studied. A rapid method for the determination of papaverine in plasma by h.p.l.c. has been described.45... 

NE is synthesized by tyrosine hydroxylation (meta ring position) followed by decarboxylation and side chain p carbon hydroxylation. The synthesis of this catecholamine is regulated by tyrosine hydroxylase. Tyrosine hydroxylation is also a key step in the synthesis of two other important catecholamines, dopamine and epinephrine. NE is packaged via active transport into synaptic (or chromaffin) vesicles prior to release by neuronal depolarization. The effects of NE are mediated by adrenergic receptors (a or P) which are G protein coupled resulting in either increases or decreases in smooth muscle tone as well as increases in cardiac rate and contractility. These effects arise out of receptor mediated increases in intracellular Ca and activation or inhibition of various protein kinases. The effects of NE are terminated essentially as a result of its active transport into the presynaptic nerve ending via an energy and Na" dependent process which utilizes the norepinephrine transporter (NET). Ultimately, NE and other catecholamines are metabolized by monoamine oxidase (MAO) and catechol-O-methyltransferase (COMT). 

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