Effect of light on Na-Ca exchange in rod outer segments in frog.
The effect of illumination on the calcium (Ca) translocation mechanisms in isolated frog rod outer segments (ROS) was studied. The ATP-dependent Ca uptake and the Ca-Ca exchange mechanisms were unaffected by light. In contrast, we report a light-evoked Ca efflux which is mediated by the Na-Ca exchange system. The ratio of released Ca to rhodopsin bleaching was measured and the stoichiometry obtained was 5 Ca molecules released per mole of rhodopsin bleached. Concomitant to the Ca release, light induced Ca uptake, which increase the total Ca content of ROS. Physiological relevance of results to the phototransduction process is discussed.
Salceda
R
R
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D007473:Ion Channels / Q000502:physiology; D008027:Light; D008564:Membrane Potentials / Q000187:drug effects; D010786:Photoreceptor Cells / Q000502:physiology*; D011898:Ranidae; D012374:Rod Cell Outer Segment / Q000502:physiology*; D012964:Sodium / Q000378:metabolism*; D009435:Synaptic Transmission / Q000187:drug effects
D007473:Ion Channels; D000255:Adenosine Triphosphate; D012964:Sodium; D002118:Calcium