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Tightening up with endothelin.

Tightening up with endothelin

Once thought to be an inert wrapping through which blood flows, the endothelial cells lining blood vessels have attracted much scientific attention -- first in terms of fatty buildup caused by atherosclerosis, more recently as the source of substances that can constrict or relax the vessels and thus affect blood pressure. Japanese researchers now report the isolation of a "novel" 21-amino-acid peptide, which they call endothelin and describe as "one of the most potent vasoconstrictors known."

Scientists from the University of Tsukuba and the Fermentation Research Institute in Ibaraki and the University of Tokyo isolated the substance -- which causes constriction of artery strips in the laboratory -- from cultures of pig endothelial cells. The researchers report in the March 31 Nature that, after DNA cloning and sequencing experiments, they discovered that endothelin does not belong to any previously known family of peptides. It is, however, similar in structure to neurotoxins known to affect the tiny channels that allow sodium ions to cross membranes. Because the endothelin-induced vessel constriction depends on calcium flow into cells, the scientists hypothesize that the new peptide acts on calcium, rather than sodium, channels.

As John Gordon at British Biotechnology Ltd. in Oxford points out in an accompanying editorial, the Japanese results are the latest in a series of endothelial-function studies. Once "regarded as a sort of nucleated dialysis bag that lines the blood vessels," the endothelium is now known to play a more active role, says Gordon. Late last year, scientists reported on the activity of endothelium-derived relaxing factor (EDRF), which prevents constriction of blood vessels (SN: 11/28/87, p.342). At the time, scientists proposed that when atherosclerosis deposits stop EDRF from reaching muscle fibers in the walls, blood vessels may open and close in spasms -- causing blood pressure problems.

But how endothelin will fit into the complex picture of blood vessel activity in the body remains unclear, says Gordon. He cites unanswered questions about the exact site of endothelin production, as well as whether the laboratory results can be extrapolated to the in vivo situation. The Japanese group suggests that endothelin, with its longer-lasting effects, may have broader influence on the body's blood pressure, as opposed to EDRF's short-lived, more localized control.
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Title Annotation:peptide causes constriction of arteries
Publication:Science News
Date:Apr 9, 1988
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