Intra‐ and intercellular Ca2+ signaling in retinal pigment epithelial cells during mechanical stimulation

ABSTRACT The intercellular communication (IC) was investigated between cultured rat retinal pigment epithelial (RPE) cells isolated from Long‐Evans (LE) or dystrophic Royal College of Surgeons (RCS) rats and grown in solutions containing normal and high glucose concentrations, or after modulation of protein kinase C (PKC). This was performed by studying the conduction of the free Ca2+‐concentration ([Ca2 +]i) wave elicited by mechanical stimulation and by analyzing the fluorescence recovery after photobleaching (FRAP). Mechanical stimulation of LE‐RPE cells triggers Ca2+ influx, mediated by stretch‐sensitive cation channels followed byintracellular Ca2+ release. A regenerative [Ca2+]i wave was found with a lower propagation rate in RCS‐RPE cells. This rate could be increased by PKC down‐regulation. Mechanical stimulation caused a [Ca2+]i increase in the mechanically stimulated (MS) cell followed after a delay by a [Ca2+]i rise in the adjacent cell layers. The intercellular [Ca2+]i wave propagation could be blocked by gap junction blockers such as halothane or PKC activation. An inhibition of the [Ca2+]i‐wave propagation similar to that induced by halothane could be observed in cells grown in solutions containing 14 mM or higher concentrations of glucose. PKC down‐regulated cells grown in glucose‐rich medium did not develop this inhibitory effect on gap junction communication (GJC). FRAP experiments confirmed that the observed changes were consistent with a PKC‐mediated inhibitory effect of high glucose concentrations on GJC. FASEB J. 13 (Suppl.), S63–S68 (1999)