pH regulation in frog cones studied by mass receptor photoresponses from the isolated retina

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Vision Research. 1993. 33: 2181-2188

Title: pH regulation in frog cones studied by mass receptor photoresponses from the isolated retina
Author: Koskelainen, A.; Donner, K.; Lerber, T.; Hemilä, S.
Publisher: Elsevier
Date: 1993
Language: en
Number of pages: 8233431 bytes
ISSN: 0042-6989
URI: http://dx.doi.org/doi:10.1016/0042-6989(93)90098-H
http://hdl.handle.net/1975/932
Abstract: Mass cone photoresponses were recorded across the aspartate-treated frog retina under treatments chosen to affect putative pH-regulating mechanisms. The saturated response amplitude (Umax) was found to be a monotonically increasing function of perfusion pH in the range 7–8, and thus presumably of intracellular pH (pHi). Accepting that Umax can be used as an index of pH, changes, two results indicate the importance of bicarbonate transport for preventing intracellular acidification: (1) bicarbonate-buffered (6 mM HCO3− + 6 mM HEPES) perfusate increased Umax compared with nominally bicarbonate-free perfusate (12 mM HEPES); (2) the anion transport blocker DIDS (0.1 mM) caused a strong decrease in the amplitude of photoresponses. Substitution of 95 mM chloride by gluconate in the perfusing fluid boosted photoresponses indicating that at least part of the bicarbonate transport involves HCO3−/Cl− exchange. Amiloride (2mM) also caused a decrease of photoresponse amplitude, which suggests that Na+/H+ exchange contributes to pHi regulation. In all these respects, cones behaved similarly to rods. Cones differed from rods (in the intact retina) in that addition of 0.5 mM of the carbonic anhydrase inhibitor acetazolamide reduced (never augmented) photoresponses. The difference is considered in relation to the presence of carbonic anhydrase in cone, as opposed to rod, outer segments.
Subject: Cone photoreceptor
Retina
Phototransduction
pH regulation
ERG


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