Light induced sodium dependent accumulation of calcium and potassium in the extracellular space of bee retina.
Intense illumination of long duration induced a large transient increase in extracellular calcium (delta[Ca2+]o) and potassium (delta[K+]o) during and after light in bee retina when measured with ion-selective microelectrodes. Whenever a large delta[Ca2+]o appeared, it was accompanied by a transient afterdepolarization (TA). Both the increase in [Ca2+]o, [K+]o and the TA were reduced or abolished when sodium was replaced by arginine, choline or lithium (Li+) ions. At 0-Na conditions a Na independent decrease in [Ca2+]o was observed during illumination only. A pronounced transient depolarization of the photoreceptor in the dark due to transient anoxia did not result in a significant change in [Ca2+]o. In some retinae the elevated level of [K+]o after light was absent, however a small Na-dependent TA was still observed. The above findings suggest that intense long illumination induces a large Ca2+ influx into the photoreceptors which is followed by Na-dependent Ca2+ efflux due to Na-Ca exchange. The light-induced afterdepolarization arises mainly from K+ accumulation in the extracellular space but partially from the electrogenicity of Na-Ca exchange.
D000818:Animals; D001516:Bees / Q000378:metabolism*; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D005110:Extracellular Space / Q000378:metabolism; D066298:In Vitro Techniques; D008027:Light; D011188:Potassium / Q000378:metabolism*; D012160:Retina / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*; D013997:Time Factors
D012964:Sodium; D011188:Potassium; D002118:Calcium