Ca2+ mobilization and capacitative Ca2+ entry regulate DNA synthesis in cultured chick retinal neuroepithelial cells

Release of Ca2+ from intracellular Ca2+ stores (Ca2+ mobilization) and capa citative Ca2+ entry have been shown to be inducible in neuroepithelial cell s of the early embryonic chick retina. Both types of Ca2+ responses decline parallel with retinal progenitor cell proliferation. To investigate their potential role in the regulation of neuroepithelial cell proliferation, we studied the effects of 2,5-di-tert-butylhydroquinone (DBHQ), an inhibitor o f the Ca pump of intracellular Ca2+ stores, and of SK&F 96365, an inhibitor of capacitative Ca2+ entry, on DNA synthesis in retinal organ cultures fro m embryonic day 3 (E3) chicks and in dissociated cultures from E7 and E9 ch ick retinae. We demonstrate that both antagonists inhibit [H-3]-thymidine i ncorporation in a dose-dependent manner without affecting cell viability or morphology. The inhibition of [H-3]-thymidine incorporation by SK&F 96365 occurred in the same concentration range (IC50: similar to 4 mu M) as the b lockade of capacitative Ca2+ entry in the E3 retinal organ culture. At a co ncentration of 5 mu M SK&F 96365, DNA synthesis was reduced by 71, 40 and 3 2% in the E3, E7 and E9 cultures, respectively. Application of DBHQ at conc entrations which led to depletion of intracellular Ca2+ stores also inhibit ed [3H]-thymidine incorporation with IC50 values of 20-30 mu M in the diffe rent cultures. Our results suggest the involvement of Ca2+ mobilization and capacitative Ca2+ entry in the regulation of DNA synthesis in the developi ng neural retina. (C) 1999 ISDN. Published by Elsevier Science Ltd. All rig hts reserved.