Intra- and intercellular Ca2+ signaling in retinal pigment epithelial cells during mechanical stimulation.
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 by intracellular 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.
Himpens
B
B
Laboratory of Physiology, KULeuven, B-3000 Leuven, Belgium. Bernard.Himpens@med.kuleuven.ac.be
Stalmans
P
P
Gomez
P
P
Malfait
M
M
Vereecke
J
J
D000818:Animals; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling; D002450:Cell Communication; D002478:Cells, Cultured; D017629:Gap Junctions / Q000378:metabolism; D005947:Glucose / Q000494:pharmacology; D007700:Kinetics; D010812:Physical Stimulation; D010857:Pigment Epithelium of Eye / Q000166:cytology / Q000378:metabolism*; D051381:Rats; D020318:Rats, Long-Evans; D013347:Subcellular Fractions / Q000378:metabolism
D005947:Glucose; D002118:Calcium