Light-induced oxygen consumption in Limulus ventral photoreceptors does not result from a rise in the intracellular sodium concentration.
Illumination of Limulus ventral photoreceptors leads to an increase in the intracellular concentration of sodium, [Na+]i, and to an increase in the consumption of O2 (delta QO2). After a 1-s light flash, it takes approximately 480 s for [Na+]i to return to within 10% of its preillumination level, whereas delta QO2 takes approximately 90 s. Thus, the delta QO2 is complete long before [Na+]i has returned to its resting level. Pressure injection of Na+ into the cell in order to elevate [Na+]i to the same levels as attained by illumination causes a rise in [Na+]i that returns to baseline with the same time course as the light-induced rise in [Na+]i. However, the injection of Na+ does not lead to an increase of the consumption of O2. We conclude that activation of the Na pump by a rise in [Na+]i is not a factor involved in the light-induced activation of O2 consumption in these cells.
Fein
A
A
Laboratory of Sensory Physiology, Marine Biological Laboratory, Woods Hole, Massachusetts 02543.
Tsacopoulos
M
M
D000818:Animals; D002118:Calcium / Q000378:metabolism; D006737:Horseshoe Crabs; D007473:Ion Channels / Q000378:metabolism*; D007700:Kinetics; D008027:Light; D008564:Membrane Potentials; D008839:Microelectrodes; D010101:Oxygen Consumption; D010786:Photoreceptor Cells / Q000378:metabolism* / Q000528:radiation effects; D012964:Sodium / Q000378:metabolism*
D007473:Ion Channels; D012964:Sodium; D002118:Calcium