MODULATION OF RAT INCISOR ODONTOBLAST PLASMA MEMBRANE-ASSOCIATED CA2+WITH NIFEDIPINE

In addition to the Ca2+ portion freely dissociated in the cytosol, ano ther Ca2+ pool is associated with plasma membranes and intracellular o rganelle membranes. This Ca2+ portion is of importance for regulation of, among other things, the cell cycle, actin-mediated processes, and cell morphology. In the literature, dihydropyridines have been reporte d to influence this membrane-associated pool of Ca2+ under certain con ditions. The aim of this investigation was to study possible modulatio ns of plasma membrane-associated Ca2+ upon treatment with nifedipine i n vitro in a Ca2+-transporting cell, the dentin-forming odontoblast. T he membrane-associated portion of Ca2+ in dissected dentinogenically a ctive rat incisor odontoblasts was monitored by fluorescence spectroph otometry using chlortetracycline as a probe. In addition, images of ch lortetracycline-Ca2+ binding were obtained by fluorescence microscopy. It was found that membrane-associated Ca2+ decreased by the dihydropy ridine nifedipine, whereas this Ca2+ pool was unaffected by the cellul ar polarization state, which was in contrast to cytosolic free Ca2+ as measured by fura-2. The results show that the odontoblast plasma memb rane-associated Ca2+-pool can be modulated by nifedipine, thus being d ependent on the conformational state of the L-type Ca2+ channels. (C) 1998 Elsevier Science B.V. All rights reserved.