The aim of this study is to characterize the subtype of tyrosine kinase-regulated L-type Ca2+ channels in retinal pigment epithelial (RPE) cells. Ca2+ channel alpha 1D-subunits were enriched by immunoprecipitation from membrane proteins isolated from rat RPE cells. Western blot analysis of the precipitates revealed coprecipitation of pp60(c-src). In addition, in precipitates obtained with antibodies against pp60(c-src), alpha 1D-subunits were identified, The same was observed in immunoprecipitations from rat brain neurons. Tyrosine phosphorylation of alpha 1D-subunits was confirmed using anti-phosphotyrosine antibodies. Ba2+ currents through L-type channels in cultured rat RPE cells were increased by intracellular application of active pp60(c-src) (30 U/ml) (heat-inactivated pp60(c-src) had no effect). Thus, L-type channels of the neuroendocrine subtype can be expressed in epithelial tells and are activated by tyrosine kinase of the src subtype, This kind of regulation is also suggested for brain-derived neurons.