Lysolecithins as Endothelium-Dependent Vascular Smooth Muscle Relaxants that Differ from Endothelium-Derived Relaxing Factor (Nitric Oxide)
The effects of lysolecithin (lysophosphatidylcholine) derived from egg yolk as well as of synthetic lysolecithins with different aliphatic chain lengths on tension development of rabbit aortic strips were investigated. Lysolecithins caused slowly progressing, dose-dependent relaxation that was inhibited by hemoglobin, methylene blue, and nordihydroguiaretic acid. Indomethacin caused no inhibition of relaxation. The degree of relaxation was endothelium-dependent and appeared to be related to the activation of guanylate cyclase [GTP pyrophosphate-lyase (cyclizing), EC 184.108.40.206]. Superoxide dismutase failed to influence relaxation. Lysolecithins with the longest aliphatic chain were the most potent relaxants of aortic strips. The experiments suggest a role of lysolecithins through their weak detergent action on membrane dynamics of endothelial cells, resulting in the production of cyclic GMP and the relaxation of arterial smooth muscle. Lysolecithins differ in several respects from endothelium-derived relaxing factor. Endothelium-derived relaxing factor is an unstable humoral substance released from endothelium and is identical to nitric oxide, itself a labile substance causing vascular relaxation and cyclic GMP accumulation. Lysolecithins may represent a different type of endothelium-dependent muscle relaxant.
Additional Information© 1988 by the National Academy of Sciences. Communicated by George B. Koelle, July 13, 1988 (received for review March 10, 1988) We thank Ms. A. Guenther and R. Sielaff for technical assistance, and L. DeChaine and L. Olszewski for secretarial help. This work was supported by grants from The Council for Tobacco Research-USA, Inc., New York; The Margaret W. and Herbert Hoover, Jr., Foundation, Pasadena, CA; The Sam S. and Rose Stein Charitable Trust, Sandusky, OH, and The Patron Saints Foundation, Pasadena, CA. The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.
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