Document Detail


Light-induced cGMP-phosphodiesterase activity in intact rat retinal rod cells as revealed by rapid-freezing enzyme cytochemistry.
MedLine Citation:
PMID:  9881458     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Cyclic guanosine monophosphate (cGMP)-phosphodiesterase (PDE) in the outer segment of vertebrate retinal rod cells is one of key enzymes mediating phototransduction. We report here on light-induced PDE activity in intact rat retinal rod cells processed by rapid-freezing enzyme cytochemistry, a new morphological technique that is a combination of rapid-freezing, freeze-substitution fixation, and subsequent enzyme cytochemistry. This technique quickly immobilizes and preserves both enzyme activity and the cell ultrastructure in a state approximating living conditions; consequently, it has proved useful for cytochemical detection of light-induced PDE activity. Using this technique we observed that the catalytic site of PDE molecules in rapid-frozen outer segments was predominantly located in the extradiscal spaces; PDE activity was significantly greater in light than in darkness; and illumination elicited marked increases in PDE activity in dark-adapted cells. Light-induced PDE activity was first cytochemically detected after 3 s of illumination and reached a peak within 5 s, at which time it was in virtually the same as that seen in fully light adapted cells. In addition, cytochemical guanosine triphosphatase (GTPase) activity in dark-adapted cells, as well as corresponding PDE activity, increased in a time-dependent manner with illumination duration; this acceleration in GTPase activity closely paralleled the PDE activity. Thus, our results suggest, in part, the existence of reciprocal regulation of PDE and activated transducin alpha subunit, thereby modulating light adaptation in rod cells.
Authors:
T Takizawa; T Takizawa; H Iwasaki; T Saito
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of electron microscopy     Volume:  47     ISSN:  0022-0744     ISO Abbreviation:  J Electron Microsc (Tokyo)     Publication Date:  1998  
Date Detail:
Created Date:  1999-01-27     Completed Date:  1999-01-27     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  7611157     Medline TA:  J Electron Microsc (Tokyo)     Country:  JAPAN    
Other Details:
Languages:  eng     Pagination:  527-33     Citation Subset:  IM    
Affiliation:
Department of Anatomy, Jichi Medical School, Tochigi, Japan. ttakizawa@jichi.ac.jp
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MeSH Terms
Descriptor/Qualifier:
3',5'-Cyclic-GMP Phosphodiesterases / analysis,  metabolism*
Animals
Enzyme Activation
Freezing
Histocytochemistry / methods
Male
Photic Stimulation
Rats
Rats, Sprague-Dawley
Retinal Rod Photoreceptor Cells / enzymology*,  ultrastructure
Chemical
Reg. No./Substance:
EC 3.1.4.35/3',5'-Cyclic-GMP Phosphodiesterases

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


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