Lead inhibits meso-2,3-dimercaptosuccinic acid induced calcium transients in cultured rhesus monkey kidney cells.

Previously we have shown that meso-2,3-dimercaptosuccinic acid (DMSA, 15-500 microM) elicits concentration-dependent increases in intracellular calcium levels ([Ca2+]i) in untreated rhesus monkey kidney cells (LLC-MK2) (Pokorski et al., 1997, unpublished results). Little is known about the restorative effects of the chelating agent 2,3-dimercaptosuccinic acid on intracellular calcium homeostasis in the presence of lead. Lead interacts at numerous sites in Ca2+ homeostasis and may mimic Ca2+ to interfere with Ca2+-mediated intracellular signaling. To examine the effects of lead on [Ca2+]i and DMSA-induced calcium transients, LLC-MK2 were plated on 35 mm coverslip dishes (10(4) cells/dish) and pre-treated with non-cytotoxic concentrations of lead (0-100 microM) for 24 h. Cells were washed, loaded with the calcium-sensitive probe Fura-2/AM, rinsed again, and examined in loading buffer in the absence of any additional lead. Intracellular calcium was measured using a dual-wavelength calcium imaging system. Basal [Ca2+]i levels did not change between Pb-exposed (0-50 microM, 24 h) and non-lead exposed cells. In cells treated with > or = 10 microM lead for 24 h, the ability of DMSA to elicit a calcium response was blocked. These results provide evidence that pre-exposure to lead blocks the entry of extracellular calcium into LLC-MK2 cells when stimulated by specific calcium mobilizing agents.