Document Detail

Intracellular biochemical manipulation of phototransduction in detached rod outer segments.
MedLine Citation:
PMID:  2827176     Owner:  NLM     Status:  MEDLINE    
Recent progress in understanding phototransduction has come primarily from studies on cell-free systems. To investigate the transduction process under physiological conditions, a fully functional preparation of retinal rod outer segments without attached inner segments was developed that allows electrical recording of light-sensitive current during intracellular dialysis with defined solutions. No light-sensitive current is recorded from detached outer segments dialyzed with nucleotide-free solutions, whereas cells detached from the retina into Ringer's solution containing 3-isobutyl-1-methyl-xanthine (a phosphodiesterase inhibitor) develop a light-sensitive inward dark current. This indicates that there is a basal level of cGMP-specific phosphodiesterase activity in the dark. Detached outer segments dialyzed with greater than or equal to 20 microM cGMP rapidly develop a light-suppressible current. A current of similar magnitude is generated more slowly during dialysis with a 50-fold greater concentration of GTP. Apparently, cGMP can be synthesized from GTP by guanylate cyclase in the outer segment. Cells dialyzed with cGMP alone show a reduced light sensitivity that is restored to normal by addition of 20 microM GTP. This action of GTP is antagonized by guanosine 5'-[beta-thio]diphosphate. These findings are in good agreement with biochemical evidence indicating that a GTP-binding protein (transducin) plays a pivotal role in the generation of responses to light. The recovery of photocurrent following a brief flash is delayed or abolished by dialysis with solutions that lack ATP or contain guanosine 5'-[gamma-thio]triphosphate, a nonhydrolyzable GTP analog. These results support the view that both GTP hydrolysis by activated transducin and ATP-dependent phosphorylation of a rhodopsin photoproduct are necessary for termination of the transduction process.
W A Sather; P B Detwiler
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Publication Detail:
Type:  In Vitro; Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Proceedings of the National Academy of Sciences of the United States of America     Volume:  84     ISSN:  0027-8424     ISO Abbreviation:  Proc. Natl. Acad. Sci. U.S.A.     Publication Date:  1987 Dec 
Date Detail:
Created Date:  1988-02-20     Completed Date:  1988-02-20     Revised Date:  2009-11-18    
Medline Journal Info:
Nlm Unique ID:  7505876     Medline TA:  Proc Natl Acad Sci U S A     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  9290-4     Citation Subset:  IM    
University of Washington, Department of Physiology and Biophysics, Seattle, WA 98195.
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MeSH Terms
Adenosine Triphosphate / physiology
Calcium / physiology
Cyclic GMP / physiology
Electric Conductivity
Guanine Nucleotides / physiology
Guanosine Triphosphate / physiology
Membrane Proteins / physiology*
Photoreceptor Cells / physiology*
Retinal Pigments / physiology*
Rhodopsin / physiology*
Rod Cell Outer Segment / physiology*
Vision, Ocular*
Grant Support
Reg. No./Substance:
0/Guanine Nucleotides; 0/Membrane Proteins; 0/Retinal Pigments; 56-65-5/Adenosine Triphosphate; 7440-70-2/Calcium; 7665-99-8/Cyclic GMP; 86-01-1/Guanosine Triphosphate; 9009-81-8/Rhodopsin; EC 3.6.1.-/Transducin

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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