EXTRACELLULAR CATION SENSING BY THE ENTEROCYTE - PREDICTION OF A NOVEL DIVALENT-CATION RECEPTOR

We report that the divalent cation Ni2+ elicits elevations in the cyto solic free Ca2+ concentration ([Ca2+]) in cultured enterocytes. These elevations were monophasic, each response consisting of a rapid initia l transient rise of cytosolic [Ca2+] to a peak value followed by an ex ponential decline. The magnitude of the cytosolic [Ca2+] elevation var ied with the concentration of applied Ni2+. In some cells, a single ap plication of Ni2+ induced oscillatory changes in cytosolic [Ca2+]. The re was also evidence for use-dependent inactivation: a conditioning ap plication of Ni2+ substantially attenuated the response resulting from its subsequent application. Our findings thus demonstrate the existen ce of a divalent cation-sensing ''receptor'' on the enterocyte. This p utative receptor may play a role in regulating mineral absorption acro ss the enterocyte membrane. (C) 1995 Academic Press, Inc.