Hyperpolarization and relaxation of arterial smooth muscle caused by nitric oxide derived from the endothelium

Article Abstract:

The endothelium, which lines the arteries, plays an important role in the regulation of the smooth muscle of the artery. Acetylcholine is a chemical produced in the body that causes arteries to relax; this action is caused by some substance which diffuses from the endothelium into the underlying smooth muscle, and induces relaxation. This substance, called endothelium-derived relaxing factor, also causes the hyperpolarization of the smooth muscle membrane, which may be electrophysiologically measured. Several suggestions have been made in an attempt to specifically identify this relaxing factor. Although nitric oxide is one possibility, not all the evidence seems to favor this molecule. Hyperpolarization of the smooth muscle cannot be achieved by adding nitric oxide from the outside. However, it may be that intimate association between the smooth muscle and the endothelium is necessary to observe the effect of nitric oxide. To determine if nitric oxide plays such a role, investigators treated arteries with the substance N-monomethyl-L-arginine. This substance is similar to the naturally occurring amino acid L-arginine, which serves as the source for the manufacture of nitric oxide within cells. However, the chemical differences prevent nitric oxide from being made from N-monomethyl-L-arginine, and this substance actually inhibits nitric oxide production. If nitric acid plays a key role in the relaxation and hyperpolarization of arterial smooth muscle, then N-monomethyl-L-arginine should inhibit these processes. This is exactly what is observed. The results indicate that nitric oxide is very likely the endothelium-derived relaxing factor. The significance of nitric oxide in this natural regulation of the arterial muscle probably accounts for the effectiveness of nitrovasodilators, such as nitroglycerin. (Consumer Summary produced by Reliance Medical Information, Inc.)

Vascular endothelium, Smooth muscle

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Nitric oxide release from a single cell measured in situ by a porphyrinic-based microsensor

Article Abstract:

Nitric oxide (NO) being emitted by a single cell can be quantified using a novel porphyrinic microsensor. This microsensor is made up of a p-type semi-conducting polymeric porphyrin and a cationic exchanger, Nafion, placed on a heat-sharpened carbon fiber tip. Physiologists have long sought an efficient means of measuring NO, a bioregulatory molecule whose many functions include activating the endothelium-derived relaxation factor. The microsensor's high linear response rate and sensitivity qualify it to become the standard method for measuring NO.

Usage, Innovations, Biosensors, Porphyrins

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NO-independent regulatory site on soluble guanylate cyclase

Article Abstract:

Research is presented concerning the use of photoaffinity labelling to determine the location of a regulatory site for nitric oxide which exists on a heterodimeric haem protein, soluble guanylate cyclase.

Research, Analysis, Blood platelets, Letter to the Editor, Cardiovascular research

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