ATP consumption by mammalian rod photoreceptors in darkness and in light

Curr Biol. 2008 Dec 23;18(24):1917-21. doi: 10.1016/j.cub.2008.10.029. Epub 2008 Dec 11.


Why do vertebrates use rods and cones that hyperpolarize, when in insect eyes a single depolarizing photoreceptor can function at all light levels? We answer this question at least in part with a comprehensive assessment of ATP consumption for mammalian rods from voltages and currents and recently published physiological and biochemical data. In darkness, rods consume 10(8) ATP s(-1), about the same as Drosophila photoreceptors. Ion fluxes associated with phototransduction and synaptic transmission dominate; as in CNS, the contribution of enzymes of the second-messenger cascade is surprisingly small. Suppression of rod responses in daylight closes light-gated channels and reduces total energy consumption by >75%, but in Drosophila light opens channels and increases consumption 5-fold. Rods therefore provide an energy-efficient mechanism not present in rhabdomeric photoreceptors. Rods are metabolically less "costly" than cones, because cones do not saturate in bright light and use more ATP s(-1) for transducin activation and rhodopsin phosphorylation. This helps to explain why the vertebrate retina is duplex, and why some diurnal animals like primates have a small number of cones, concentrated in a region of high acuity.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate / metabolism*
  • Animals
  • Darkness
  • In Vitro Techniques
  • Ion Transport
  • Light
  • Mammals
  • Mice
  • Oxygen Consumption
  • Patch-Clamp Techniques
  • Retina / metabolism
  • Retinal Cone Photoreceptor Cells / metabolism
  • Retinal Photoreceptor Cell Inner Segment / metabolism
  • Retinal Rod Photoreceptor Cells / metabolism*
  • Retinal Rod Photoreceptor Cells / radiation effects*
  • Rod Cell Outer Segment / metabolism
  • Sodium-Potassium-Exchanging ATPase / metabolism


  • Adenosine Triphosphate
  • Sodium-Potassium-Exchanging ATPase