The effect of sodium ions on the light-induced 86Rb release from the isolated crayfish retina.
The effect of low external Na+ concentrations on the light-induced K+ release from crayfish photoreceptor cells was tested by labelling intracellular K+ with the isotope 86Rb. The amount of isotope released per light stimulus is roughly proportional to the external Na+ concentration if the osmolarity is kept constant by replacing Na+ with Tris, choline or sucrose. When sucrose is used to replace the depleted Na+ the light-induced K+ release is a linear function of the external Na+ concentration and is reduced by approx. 95% at an external Na+ concentration of 5 mmol/l. For choline and Tris substitutions the relationships are less clear but at Na+ concentrations less than or equal to 56 mmol/l it seems that in comparison with sucrose the light-induced K+ release is smaller in a Tris solution and larger in a choline solution. It is suggested that the light-induced K+ release is due mainly to an activation of voltage sensitive K+ channels.
D000818:Animals; D003400:Astacoidea / Q000502:physiology*; D066298:In Vitro Techniques; D008027:Light; D011868:Radioisotopes; D012160:Retina / Q000378:metabolism* / Q000528:radiation effects; D012413:Rubidium / Q000378:metabolism*; D012964:Sodium / Q000502:physiology*
D011868:Radioisotopes; D012964:Sodium; D012413:Rubidium