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Coupling between Transmembrane Calcium Transport and Membrane Potential in Retinal Rod Discs

I. D. Volotovski and V. I. Khovratovich
Proceedings of the Royal Society of London. Series B, Biological Sciences
Vol. 228, No. 1250 (Jun. 23, 1986), pp. 97-108
Published by: Royal Society
Stable URL: http://www.jstor.org/stable/36139
Page Count: 12
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Coupling between Transmembrane Calcium Transport and Membrane Potential in Retinal Rod Discs
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Abstract

Changes in the transmembrane potential of bovine rod discs were studied by use of the potential-sensitive fluorescence probes diS-C3-(5) and diBA-C4-(5). The disc membrane was shown to be impermeable to potassium ions. Their concentration in the disc is as high as 2.1 ± 0.3 mM. The permeability of the disc membrane to Ca2+ was shown to be selective. The accumulation and release of Ca2+ were found to be accompanied by the generation of inside positive and inside negative transmembrane potentials, respectively. The uptake of Ca2+ in the discs may operate against the concentration gradient of the ion. The value of the potential developed is directly proportional to the logarithm of free Ca2+ concentration in the medium (Δ φ m = 11.2 ± 1.6 mV at 4.85 μ M Cafr 2+). The accumulation of Ca2+ is decreased by sodium ions and totally inhibited by monensin. This indicates that a Na-Ca exchange process participates in Ca2+ uptake of photoreceptor discs.

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