| 3',5'-cyclic adenosine monophosphate and adenylate cyclase in phototransduction by limulus ventral photoreceptors. | |
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MedLine Citation:
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PMID: 6207288 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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Biochemical and electrophysiological measurements were made on photoreceptor cells from Limulus ventral eyes to investigate the possible role of cyclic AMP and adenylate cyclase in the visual transduction mechanism. Cyclic AMP content in a photoreceptor-enriched fraction (the end organs) of Limulus ventral eyes was approximately 15 pmol/mg protein. The cyclic AMP content was increased by bathing eyes in 1-methyl-3-isobutyl xanthine or forskolin and was increased almost 100-fold when bathed in both. Illumination did not change cyclic AMP content significantly in any of these conditions. Discrete events that can be recorded electrophysiologically occur spontaneously in darkness. An increase in the frequency of discrete events is evoked by dim illumination. The discrete events are a sign of excitation of Limulus photoreceptor cells. Drug-induced changes in the rate of occurrence of discrete events recorded electrophysiologically in darkness were not correlated with changes in cyclic AMP content. Adenylate cyclase activity measured from a small number of pooled photoreceptor clusters was stimulated by fluoride and vanadate ions, hydrolysis-resistant analogues of GTP, cholera toxin and forskolin. The Limulus enzyme is similar pharmacologically to mammalian and avian adenylate cyclases. Activation of adenylate cyclase by drugs was not correlated with changes in the rate of occurrence of discrete events recorded electrophysiologically in darkness. A heat-treated Lubrol extract of membranes from Limulus ventral eyes reconstituted the adenylate cyclase activity of membranes from S49 mouse lymphoma cyc- mutant cells which lack a functional regulatory protein. These findings suggest that Limulus ventral eye photoreceptors contain a regulatory protein that mediates the activation of adenylate cyclase by guanine nucleotides, fluoride or cholera toxin. This regulatory protein is homologous with that found in mammalian and avian adenylate cyclases. Our findings suggest that neither cyclic AMP nor adenylate cyclase activation is a necessary or obligatory component of the excitation mechanism in Limulus ventral photoreceptors. |
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Authors:
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J E Brown; U B Kaupp; C C Malbon |
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Publication Detail:
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Type: In Vitro; Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S. |
Journal Detail:
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Title: The Journal of physiology Volume: 353 ISSN: 0022-3751 ISO Abbreviation: J. Physiol. (Lond.) Publication Date: 1984 Aug |
Date Detail:
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Created Date: 1984-11-14 Completed Date: 1984-11-14 Revised Date: 2009-11-18 |
Medline Journal Info:
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Nlm Unique ID: 0266262 Medline TA: J Physiol Country: ENGLAND |
Other Details:
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Languages: eng Pagination: 523-39 Citation Subset: IM |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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1-Methyl-3-isobutylxanthine
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pharmacology Action Potentials / drug effects Adenylate Cyclase / metabolism* Animals Cholera Toxin / pharmacology Cyclic AMP / metabolism* Cyclic GMP / metabolism Diterpenes / pharmacology Fluorides / pharmacology Forskolin Horseshoe Crabs / metabolism, physiology* Light Photoreceptor Cells / metabolism, physiology* Time Factors Vanadates Vanadium / pharmacology |
| Grant Support | |
ID/Acronym/Agency:
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AM-30111/AM/NIADDK NIH HHS; EY-01914/EY/NEI NIH HHS; EY-01915/EY/NEI NIH HHS |
| Chemical | |
Reg. No./Substance:
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0/Diterpenes; 0/Fluorides; 0/Vanadates; 28822-58-4/1-Methyl-3-isobutylxanthine; 60-92-4/Cyclic AMP; 66428-89-5/Forskolin; 7440-62-2/Vanadium; 7665-99-8/Cyclic GMP; 9012-63-9/Cholera Toxin; EC 4.6.1.1/Adenylate Cyclase |
| Comments/Corrections | |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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