Regulation of capacitative Ca2+ entry by tyrosine phosphorylation in the neural retina of chick embryo

Capacitative Ca2+ entry occurs in the neural retina of chick embryo during neurogenesis. We studied the effects of blockers of capacitative Ca2+ entry (SK&F 96365, Zn2+, Ni2+), genistein, a tyrosine kinase inhibitor and vanad ate, a protein-phosphotyrosine phosphatase inhibitor in the embryonic chick retina with fura-2 fluorescence measurements. After incubation of the reti na in a Ca2+-free solution with or without an inhibitor of Ca2+ pumps of in tracellular Ca2+ stores, re-introduction of extracellular Ca2+ caused capac itative Ca2+ entry which was inhibited by SK&F 96365 (10 mu M), Zn2+ (1 mM) , Ni2+ (5 mM) and genistein (100 mu M). On the contrary, vanadate (1 mM) en hanced the Ca2+ entry. These results suggested that tyrosine phosphorylatio n was involved in the activation of capacitative Ca2+ entry. (C) 1999 Elsev ier Science Ireland Ltd. All rights reserved.