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Bleached pigment activates transduction in salamander cones

We have used suction electrode recording together with rapid steps into 0.5 mM IBMX solution to investigate changes in guanylyl cyclase velocity produced by pigment bleaching in isolated cones of the salamander Ambystoma tigrinum. Both backgrounds and bleaches accelerate the time course of current i...

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Formato: Texto
Lenguaje:English
Publicado: The Rockefeller University Press 1995
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2229273/
https://www.ncbi.nlm.nih.gov/pubmed/8786347
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collection PubMed
description We have used suction electrode recording together with rapid steps into 0.5 mM IBMX solution to investigate changes in guanylyl cyclase velocity produced by pigment bleaching in isolated cones of the salamander Ambystoma tigrinum. Both backgrounds and bleaches accelerate the time course of current increase during steps into IBMX. We interpret this as evidence that the velocity of the guanylyl cyclase is increased in background light or after bleaching. Our results indicate that cyclase velocity increases nearly linearly with increasing percent pigment bleached but nonlinearly (and may saturate) with increasing back-ground intensity. In cones (as previously demonstrated for rods), light-activated pigment and bleached pigment appear to have somewhat different effects on the transduction cascade. The effect of bleaching on cyclase rate is maintained for at least 15-20 min after the light is removed, much longer than is required after a bleach for circulating current and sensitivity to stabilize in an isolated cone. The effect on the cyclase rate can be completely reversed by treatment with liposomes containing 11-cis retinal. The effects of bleaching can also be partially reversed by beta-ionone, an analogue of the chromophore 11- cis-retinal which does not form a covalent attachment to opsin. Perfusion of a bleached cone with beta-ionone produces a rapid increase in circulating current and sensitivity, which rapidly reverses when the beta-ionone is removed. Perfusion with beta-ionone also causes a partial reversal of the bleach-induced acceleration of cyclase velocity. We conclude that bleaching produces an "equivalent background" excitation of the transduction cascade in cones, perhaps by a mechanism similar to that in rods.
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spelling pubmed-22292732008-04-23 Bleached pigment activates transduction in salamander cones J Gen Physiol Articles We have used suction electrode recording together with rapid steps into 0.5 mM IBMX solution to investigate changes in guanylyl cyclase velocity produced by pigment bleaching in isolated cones of the salamander Ambystoma tigrinum. Both backgrounds and bleaches accelerate the time course of current increase during steps into IBMX. We interpret this as evidence that the velocity of the guanylyl cyclase is increased in background light or after bleaching. Our results indicate that cyclase velocity increases nearly linearly with increasing percent pigment bleached but nonlinearly (and may saturate) with increasing back-ground intensity. In cones (as previously demonstrated for rods), light-activated pigment and bleached pigment appear to have somewhat different effects on the transduction cascade. The effect of bleaching on cyclase rate is maintained for at least 15-20 min after the light is removed, much longer than is required after a bleach for circulating current and sensitivity to stabilize in an isolated cone. The effect on the cyclase rate can be completely reversed by treatment with liposomes containing 11-cis retinal. The effects of bleaching can also be partially reversed by beta-ionone, an analogue of the chromophore 11- cis-retinal which does not form a covalent attachment to opsin. Perfusion of a bleached cone with beta-ionone produces a rapid increase in circulating current and sensitivity, which rapidly reverses when the beta-ionone is removed. Perfusion with beta-ionone also causes a partial reversal of the bleach-induced acceleration of cyclase velocity. We conclude that bleaching produces an "equivalent background" excitation of the transduction cascade in cones, perhaps by a mechanism similar to that in rods. The Rockefeller University Press 1995-09-01 /pmc/articles/PMC2229273/ /pubmed/8786347 Text en This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.rupress.org/terms). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 4.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/4.0/).
spellingShingle Articles
Bleached pigment activates transduction in salamander cones
title Bleached pigment activates transduction in salamander cones
title_full Bleached pigment activates transduction in salamander cones
title_fullStr Bleached pigment activates transduction in salamander cones
title_full_unstemmed Bleached pigment activates transduction in salamander cones
title_short Bleached pigment activates transduction in salamander cones
title_sort bleached pigment activates transduction in salamander cones
topic Articles
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2229273/
https://www.ncbi.nlm.nih.gov/pubmed/8786347