A quantitative estimate of flash-induced Ca(2+)- and Na(+)-influx and Na+/Ca(2+)-exchange in blowfly Calliphora photoreceptors.
The flash-induced Ca(2+)- and Na(+)-influx and Na+/Ca(2+)-exchange activity in blowfly Calliphora photoreceptors were investigated. The change in membrane potential, induced by a bright flash, was intracellularly measured in vivo. Based on a biophysical photoreceptor model, the Na(+)- and Ca(2+)-currents and concentration changes were determined from the first transient depolarization phase of the photoreceptor response. The activity of Na+/Ca(2+)-exchange was determined from the after depolarization phase. It appeared that the Na(+)-influx by Na+/Ca(2+)-exchange is about twice that through light-activated channels, suggesting a substantial contribution of Na+/Ca(2+)-exchange to Na(+)-regulation.
Gerster
U
U
Free University of Berlin, Germany. uli.gerster@uibk.ac.au
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D004175:Diptera / Q000502:physiology*; D007473:Ion Channels / Q000528:radiation effects; D008433:Mathematics; D008564:Membrane Potentials / Q000528:radiation effects; D008954:Models, Biological; D010775:Photic Stimulation; D017956:Photoreceptor Cells, Invertebrate / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*; D013997:Time Factors
D007473:Ion Channels; D012964:Sodium; D002118:Calcium