Nitric Oxide Function in an Echinoderm

In vertebrates, nitric oxide (NO) is synthesized from L-arginine by NO synthase (NOS) and regulates relaxation of smooth muscle by activating the cyclic-GMP (cGMP) generating enzyme soluble guanylyl cyclase (SGC). Here we show that the NO-cGMP pathway mediates relaxation of the cardiac stomach in th...

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Published inThe Biological bulletin (Lancaster) Vol. 194; no. 3; pp. 260 - 266
Main Authors Elphick, Maurice R., Melarange, Richard
Format Journal Article
LanguageEnglish
Published United States Marine Biological Laboratory 01.06.1998
University of Chicago Press
Subjects
Aquatic life
Asterias rubens
Biology
Cyclic guanosine monophosphate
Cyclic guanylic acid
Echinodermata
Echinoderms
Enzymes
Heart
Marine
Muscle tonus
Muscles
Neurobiology and Behavior
Neurons
Nitric oxide
Oxides
Physiological aspects
Physiological regulation
Smooth muscle
Starfish
Starfishes
Stomach
Vertebrates
Washing
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Summary:In vertebrates, nitric oxide (NO) is synthesized from L-arginine by NO synthase (NOS) and regulates relaxation of smooth muscle by activating the cyclic-GMP (cGMP) generating enzyme soluble guanylyl cyclase (SGC). Here we show that the NO-cGMP pathway mediates relaxation of the cardiac stomach in the starfish Asterias rubens. The NO-donors hydroxylamine, S-nitrosoglutathione (SNOG) and S-nitroso-N-acetylpenicillamine (SNAP) and the NOS substrate L-arginine cause relaxation of the cardiac stomach. The relaxing effect of SNAP is blocked by the SGC inhibitor 1H-[1,2,4]-oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), and the relaxing effect of L-arginine is inhibited by ODQ and the NOS inhibitor Nω-monomethyl-L-arginine (L-NMMA). ODQ and methylene blue also cause contraction, which may be due to inhibition of the relaxing action of NO produced by cells in the cardiac stomach. These results suggest that NO is synthesized in the cardiac stomach and regulates relaxation by activating SGC. NO-cGMP-mediated relaxation of the cardiac stomach may be important during feeding in starfish where the relaxed stomach is everted through an oral opening and over the digestible parts of prey. The discovery of NO-cGMP-mediated relaxation in an echinoderm demonstrates that regulation of smooth muscle tone by this signaling pathway also occurs in animals other than vertebrates.
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ISSN:0006-3185
1939-8697
DOI:10.2307/1543096