Changes in intracellular calcium ion concentration, in the course of dark adaptation measured by Arsenazo III in the Limulus photoreceptor (original) (raw)

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Abstract

In experiments on the ventral nerve photoreceptor cells in Limulus the transient absorption changes of the intracellularly pressure-injected calcium indicator dye, Arsenazo III which were evoked by 10 ms intense light flashes were recorded at 645 nm together with the corresponding receptor potential. The Arsenazo signal provided a monitor of the intracellular calcium ion concentration during different experimental conditions.

    1. The time between the peak of the Arsenazo signal and that of the receptor potential was shorter (ca. 50 ms) when small amounts of Arsenzo where injected into the cell. This indicates that there may be little or no delay between membrane voltage signal and increase in intracellular calcium.
    1. Results obtained under voltage clamp conditions show that the Arsenazo signal depends on the membrane potential. Plotting the amplitude of the Arsenazo signal as function of the time integral of the light induced membrane current signal (which corresponds to the bulk of tranported charge), results in a linear proportionality. This may indicate that the light induced increase in intracellular calcium is due to a constant fraction of the ion current underlying the receptor current.
    1. During the time course of dark adaptation following a light adapting flash, two phases of recovery of the amplitude hinT, of the time integral of the receptor potential and of the amplitude AinT of the Arsenazo signal evoked by a constant test flash can be seen (Fig. 5). The first phase correlates with the decrease of the prestimulus level A P of the intracellular calcium ion concentration which had been raised due to the light adaptation. The recovery of the amplitude of the Arsenazo signal and the time integral of the receptor potential appear to be similar both in time course and in relative amplitude of the two phases whereas the recovery of the height hinT of the receptor potential seems to be attenuated in the second phase.

This two-phase recovery indicates the operation of two mechanisms regulating the sensitivity of the photoreceptor. Only the first phase seems to be strongly correlated with the decline of the intracellular calcium ion concentration.

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  1. K. Nagy
    Present address: I. Physiologisches Institut der UniversitÄt des Saarlandes, D-6650, Homburg/Saar, Germany

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  1. Institut für Neurobiologie der Kernforschungsanlage Jülich GmbH, Postfach 19 13, D-5170, Jülich, Germany
    K. Nagy & H. Stieve

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  1. K. Nagy
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  2. H. Stieve
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Nagy, K., Stieve, H. Changes in intracellular calcium ion concentration, in the course of dark adaptation measured by Arsenazo III in the Limulus photoreceptor.Biophys. Struct. Mechanism 9, 207–223 (1983). https://doi.org/10.1007/BF00537817

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