Light-dependent ion influx into toad photoreceptors.
Open Access
- 1 October 1982
- journal article
- research article
- Published by Rockefeller University Press in The Journal of general physiology
- Vol. 80 (4), 517-536
- https://doi.org/10.1085/jgp.80.4.517
Abstract
To measure the influx of Na+ and other ions through the light-dependent permeability of photoreceptors, we superfused the isolated retina of the toad, Bufo marinus, with a low-Ca2+ (10(-8) M), low-Cl- Ringer's solution containing 0.5 mM ouabain. Under these conditions, the membrane potential of the rod is near zero and there is no light-induced potential change either in the rod or in more proximal neurons. The photoreceptors, however, continue to show a light-dependent increase in membrane resistance, which indicates that the light-sensitive channels still close with illumination. Dark-adapted retinas show a larger 22Na+ accumulation than do light-adapted retinas. The extra accumulation of 22Na+ into dark-adapted retinas can be removed if the retinas are washed in darkness with low-Ca2+ Ringer's solutions, or if the ionophore gramicidin D is present in the perfusate. The additional accumulation in dark retinas corresponds to a flux of at least 10(9) Na+ per receptor per second, which is close to the value of the photoreceptor dark current. The light-dependent uptake of 22Na+ can be prevented by exposing the retinas to Ca2+ during the incubation period, but is restored if the phosphodiesterase inhibitor IBMX is added to the perfusate. A significant light-dependent ion accumulation can be observed for the cations K+, Rb+, Cs+, and Tl+, in addition to Na+, but not for methylamine, choline, or tetraethylammonium.This publication has 9 references indexed in Scilit:
- Ca2+-dependent changes in cyclic GMP levels are not correlated with opening and closing of the light-dependent permeability of toad photoreceptors.The Journal of general physiology, 1982
- Effect of ions on the light-sensitive current in retinal rodsNature, 1981
- Ion selectivity of the cation transport system of isolated intact cattle rod outer segments. Evidence for a direct communication between the rod plasma membrane and the rod disk membranesBiochimica et Biophysica Acta (BBA) - Biomembranes, 1980
- Light adaptation in toad rods: requirement for an internal messenger which is not calcium.The Journal of Physiology, 1979
- Cyclic GMP and the permeability of the disks of the frog photoreceptors.The Journal of Physiology, 1979
- Sensitivity of toad rods: Dependence on wave‐length and background illumination.The Journal of Physiology, 1976
- Sodium channel selectivity. Dependence on internal permeant ion concentration.The Journal of general physiology, 1976
- Biochemical correlates of adaptation processes in isolated frog photoreceptor membranes.The Journal of general physiology, 1976
- PROTEIN MEASUREMENT WITH THE FOLIN PHENOL REAGENTJournal of Biological Chemistry, 1951