Relaxation of smooth muscles

Many compounds contain more than one functional group Prostaglandin Ei a hormone that regulates the relaxation of smooth muscles con tains two different kinds of carbonyl groups Classify each one (aldehyde ketone carboxylic acid ester amide acyl chloride or acid anhydride) Identify the most acidic proton in prostaglandin Ei and use Table 1 7 to estimate its pK ... 

Three years later Robert F Furchgott discov ered that the relaxing of smooth muscles such as blood vessel walls was stimulated by an unknown substance produced in the lining of the blood vessels (the endothelium) He called this substance the endothelium-dependent relaxing factor or EDRF and in 1986 showed that EDRF was NO Louis J Ignarro reached the same conclusion at about the same time Further support was provided by Salvador Moncada who showed that endothelial cells did in deed produce NO and that the l arginine to l citrulline conversion was responsible... 

In addition, vinpocetine selectively inhibits a specific calcium, calmodulin-dependent cycHc nucleotide phosphodiesterase (PDF) isozyme (16). As a result of this inhibition, cycHc guanosine 5 -monophosphate (GMP) levels increase. Relaxation of smooth muscle seems to be dependent on the activation of cychc GMP-dependent protein kinase (17), thus this property may account for the vasodilator activity of vinpocetine. A review of the pharmacology of vinpocetine is available (18). 

As noted above, g-adrenergic agonists such as epinephrine typically cause relaxation of smooth muscle. This agent... 

Smooth Muscle Tone Regulation. Figure 3 Major mechanisms leading to relaxation of smooth muscle. See text for the abbreviations. 

Respiratory frarf—drying of the secretions of the mouth, nose, throat, bronchi, relaxation of smooth muscles of the bronchi resulting in slight bronchodilatation... 

Intoxication with amyl nitrite or butyl nitrite (i.e., poppers) is characterized by euphoria, warm feelings, change in perception of time, a sense of fullness in the head, relaxation of smooth muscle, vasodilatation, increased heart rate, and decreased systolic blood pressure. An increase in sexual drive and intensification of orgasm, poor judgment, and a reduction in inhibitions are... 

Another noteworthy example of the relaxation of smooth muscle by way of P2-receptor stimulation involves airways. Bronchodilation, or opening of the airways, facilitates airflow in the lungs. Any direct sympathetic innervation to the lungs is irrelevant in this respect because only circulating... 

Significant relaxation of smooth muscle of both venules and arterioles is produced by which of the following drugs ... 

Only a few ahphatic fluoro-nitro compounds have been examined, and if n is odd the material is toxic. Having regard, however, to the known relaxation of smooth muscle, irrespective of the type of innervation, by the nitrite ion, the writer feels that caution is required in drawing conclusions regarding the toxic action of fluoro-nitro compounds. 

Furthermore, as well as CaCM-induced phosphorylation, MLCK is also subject to control via a cAMP-dependent protein kinase, PKA. Phosphorylated MLCK binds CaCM only weakly, thus contraction is impaired. This explains the relaxation of smooth muscle when challenged with adrenaline (epinephrine), a hormone whose receptor is functionally linked with adenylyl cyclase (AC), the enzyme that generates cAMP from ATP. 

Vasoactive Intestinal VIP, (VPAC,) Human cDNA Asthma, hypertension, gastrointestinal disorders, inflammation, septic shock, diabetes Relaxation of smooth muscle, immune modulator, neuroprotection... 

Cyclic GMP lowers intracellular calcium, leading to (1) release of sodium in kidney cells or (2) relaxation of smooth muscle in blood vessels. 

Penile erection is essential for insertion of the penis into the vagina and therefore is essential for reproduction. This process depends upon relaxation of smooth muscle in the... 

Figure 19.18 The role of cyclic GMP and vasodilation in provision and preparation of spermatozoa for fertilisation. Vasodilation is regulated by the concentration of cyclic GMP by relaxation of smooth muscle. The resultant increase in blood flow to the corpora cavernosa results in erection of the penis for the ejaculation of spermatozoa into the vagina. The increase in blood flow to the vaginal smooth muscle provides more oxygen for diffusion into the lumen. Here it provides for oxidative phosphorylation in the mitochondria of the-mid section of the spermatozoa, which provides the ATP for the beating of the flagellum and hence for swimming to the oviduct for fertilisation.

Major effector proteins for G-pro-tein-coupled receptors include adenylate cyclase (ATP intracellular messenger cAMP), phospholipase C (phos-phatidylinositol intracellular messengers inositol trisphosphate and di-acylglycerol), as well as ion channel proteins. Numerous cell functions are regulated by cellular cAMP concentration, because cAMP enhances activity of protein kinase A, which catalyzes the transfer of phosphate groups onto functional proteins. Elevation of cAMP levels inter alia leads to relaxation of smooth muscle tonus and enhanced contractility of cardiac muscle, as well as increased glycogenolysis and lipolysis (p. 

Drugs of this group are calcium channel blockers that inhibit slow transmembrane calcium ion flow in the cell of the conductive system of the heart during depolarization, which causes a slowing of atrioventricular conductivity and increased effective refractive period of atrioventricular ganglia, which eventually leads to the relaxation of smooth muscle of heart musculature and restores normal sinus rhythm during supraventricular tachycardias. 

Diazoxide is a nondiuretic derivative of thiazides that dramatically reduces blood pressure by direct relaxation of smooth muscles of the arterioles, possibly as a result of calcium... 

The effect of a given adrenomimetic drug on a particular type of effector cell depends on the receptor selectivity of the drug, the response characteristics of the effector cells, and the predominant type of adrenoceptor found on the cells. For example, the smooth muscle cells of many blood vessels have only or predominantly a-adrenoceptors. The interaction of compounds with these adrenoceptors initiates a chain of events in the vascular smooth muscle cells that leads to activation of the contractile process. Thus, norepinephrine and epinephrine, which have high affinities for a-adrenoceptors, cause the vascular muscle to contract and the blood vessels to constrict. Since bronchial smooth muscle contains p2-adrenoceptors, the response in this tissue elicited by the action of p2-adrenoceptor agonists is relaxation of smooth muscle cells. Epinephrine and isoproterenol, which have high affinities for p2-adrenoceptors, cause relaxation of bronchial smooth muscle. Norepinephrine has a lower affinity for p2-adrenoceptors and has relatively weak bronchiolar relaxing properties. 

GIT Adrenaline causes relaxation of smooth muscles of GIT and reduce its motility. Relaxation of smooth muscles of GIT can be brought about by both alpha and beta stimulants. It decreases the tone, frequency and amplitude of contraction of smooth muscles. 

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