EXPRESSION OF EXTRACELLULAR CALCIUM-SENSING RECEPTOR BY HUMAN LENS EPITHELIAL-CELLS

The extracellular calcium-sensing receptor (CaR) confers the capacity to sense small changes in the extracellular Ca2+ concentration (Ca-0(2 +)) not only upon cells involved in maintaining systemic Ca2+ homeosta sis but also upon those not directly involved in this process. Since h igh Ca-0(2+) is known to affect various physiological processes in len s epithelium both in health and in disease states (e.g., the formation of cataracts in hypocalcemic states), we investigated the expression and function of the CaR in these cells. By RT-PCR and immunocytochemis try the CaR is expressed in human lens epithelial cells in culture. In addition, the open state probability of a Ca2+-activated potassium (K +) channel with a conductance of 82 +/- 3 pS is significantly increase d by elevating Ca-0(2+) to 3.0 mM or by application of 100 mu M neomyc in, both effective CaR agonists. Therefore, our data suggest that huma n lens epithelial cells express the CaR, which may be functionally lin ked to Ca2+-activated K+ channels and, perhaps, to other ion channels involved in ionic homeostasis in the lens. (C) 1997 Academic Press.