Studies on the electrolyte transport in corneal cells.

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The transparency of the cornea is very important for the maintenance of good visual function. Normal functional state of corneal epithelial cells as well as endothelial cells are important for the corneal transparency. In this study we have investigated endothelin-induced mitogenesis and the second messenger systems working in cultured rabbit corneal epithelial cells.We have clearly demonstrated the following :1) Cultured rabbit corneal endothelial cells produce endothelin. The occurrence of mRNA for prepro-endothelin was found by reverse transcription initiated polymerase chain reaction. In the culture supernatant of the rabbit corneal epithelial cells, radioreactive endothelin was found.2) Endothelin dose-dependently increases mitogenesis of cultured rabbit corneal epithelial cells. Endothelin 1 dose-dependently increased (EC50 = 0.3 nM) 3H-thymidine uptake of the cell up to 200% of the control. Endothelin was shown to be a comitogen because coexistence of low concentration of fetal bovine serum increased the mitogenic effect.3) Endothelin increases intracellular cytosolic Ca^<2+> concentration in the cell. Endothelin, at 100 nM, increased cytosolic free Ca^<2+> concentration by more than 200 nM. This phenomenon was preceded by PI turnover.