Calcium Transport by Primary Cultured Neuronal and Glial Cells from Chick Embryo Brain

Abstract

The uptake of Ca was examined in primary cultures of pure neurons and of glial cells from dissociated hemispheres of chick embryo brain. Neuronal cultures took up Ca at a rate of 2.0 nmol/min per mg cell protein at medium concentrations of 1.2 mM-Ca2+ and 5.4 mM-K+. The rate of Ca entry into neurons was increased 2.7-fold by elevating medium K to 60 mM. The effect of high external K was to increase the Vmax value for Ca transport from 5.5-13 nmol/min per mg; the Km for Ca, 1.2 mM, was unchanged. The K-dependent component of Ca entry into the neuronal cultures was eliminated by addition of 0.1 mM-D-600 (methoxy verapamil) or by 1 mM-CoCl2; 0.5 .mu.M-tetrodotoxin had no significant effect. When choline replaced K in uptake medium no change in Ca transport was detected in neurons and the entry of Ca was not increased when choline replaced Na. Glial cultures took up Ca at 20% of the basal rate for neuronal cultures on a weight-of-protein basis. Uptake was not increased by K; during depolarization by K the Ca transport activity of glia was < 10% that of neurons. Cultured neurons apparently contain a depolarization-sensitive, Ca-specific channel. A similar Ca transport activity was not detected in cultured glial cells.