CAPACITATIVE CA2-EMBRYO( INFLUX IN THE NEURAL RETINA OF CHICK)

Depletion of intracellular Ca2+ stores induces a capacitative Ca2+ inf lux in non-neural cells, It has been unknown whether the capacitative Ca2+ influx occurs in the cells of nervous systems, We found the capac itative Ca2+ influx in the neural retina of early embryonic chick with Fura-2 fluorescence measurements, a Ca2+-free medium containing thaps igargin (500 nM), an inhibitor of Ca2+-ATPase of intracellular Ca2+ st ores, was applied to the neural retina of embryonic day 3 (E3) chick, A rise in intracellular Ca2+ concentration was evoked after the reintr oduction of extracellular Ca2+, and this Ca2+ rise was suppressed by Z n2+ (1 mM) and Ni2+ (5 mM). The developmental changes in the Ca2+ rise induced by thapsigargin (250 nM) were studied from E3 to E13, The tha psigargin-induced Ca2+ rise was largest at E3, decIined rapidly toward E6, and then decreased gradually until E13, when the Ca2+ rise almost disappeared. This de developmental profile correlated with the declin e in the mitotic activities of the retinal cells studied by Prada et a l, The fluorescence imaging with the vertical slice of the E9 retina s howed that the site at which the thapsigargin-induced Ca2+ rise was la rgest was the most outer layer of the retina, where proliferating cell s are located. This spatial distribution and the above developmental p rofile may suggest that the capacitative Ca2+ influx occurs at the ear ly period of neurogenesis when the cells have mitotic activities. (C) 1997 John Wiley & Sons, Inc.