The retinal pigment epithelium (RPE) fulfills a multitude of tasks in maintaining normal retinal function. It is known that these tasks are regulated by changes of the intracellular Ca²⁺ concentration. However, the diversity of Ca²⁺ transporting membrane proteins in the RPE is hardly investigated. Therefore, we investigated the expression profile of possible Ca²⁺ channels in the RPE.

We found a variety of Ca²⁺ channels to be expressed in the RPE. Besides all four L type Ca²⁺ channel subunits two T type subunits could be detected. Additionally, two subunits of the cyclic nucleotide-gated channels are expressed in the RPE. The transient receptor potential channels (TRP) are subdivided into 6 subgroups. Altogether transcripts for 15 members of 5 subfamilies were found in the RPE. The family of ATP-gated ion channels (P2XR) is represented by 5 members. Apart from some differences freshly isolated and ARPE-19 cells have very similar expression patterns.

The complex pattern of Ca²⁺ signalling in the RPE is reflected by the expression of great diversity of Ca²⁺ channels. With their different activation mechanisms, such as voltage, cyclic nucleotides, ATP, temperature, etc., the RPE is able to react to different environmental changes by changes in the intracellular Ca²⁺ concentration.