EXTRACELLULAR PH MODULATES ALUMINUM-BLOCKADE OF MAMMALIAN VOLTAGE-ACTIVATED CALCIUM-CHANNEL CURRENTS

THE pH-dependence of aluminium (Al) blockade of voltage activated calc ium channels (VACCs) was investigated. Using cultures of rat dorsal ro ot ganglion (DRG) neurones, whole-cell patch-clamp experiments were pe rformed. Various concentrations of Al were extracellularly applied wit hin solutions of different pH-values. The block of VACC currents was h ighly pH-dependent. At pH 7.3-7.8, the concentration-response curve sh ifted slightly to higher concentrations, whereas at pH 6.4-6.9 a prono unced shift to lower concentrations was observed. This effect could be due to changes of the chemical equilibria of the different Al species or to altered properties of the VACCs. Thus, pH-shifts may influence the interactions of Al with VACCs making them more susceptible to the effects of Al and therefore contribute to its toxicity.