EXTRACELLULAR-MATRIX PROTEINS AS SUBSTRATE MODULATE THE PATTERN OF CALCIUM-CHANNEL EXPRESSION IN CULTURED RAT RETINAL-PIGMENT EPITHELIAL-CELLS

We investigated the effect of different culture substrates on the expression of membrane conductances for calcium in cultured rat retinal pigment epithelial (RPE) cells using the perforated patch technique and barium as charge carrier. In younger cultures (up to 12 days old) the RPE cells expressed L-type calcium channels, in older cultures (more than 12 days old) LVA-type channels. The LVA-type channels have been characterized as a tetrodotoxin sensitive Ca2+ channels. Coating the culture substrate with laminin, shifted the culture age for expression of LVA-type channels to 7 days. When collagen type 4 was used as substrate LVA-type channels and L-type channels were expressed simultaneously in 7 days old cultures. We concluded that proteins of the extracellular matrix which are known to enhance cell differentiation in culture, enhance the expression of LVA-type channels in RPE cells.