Meso-2,3-Dimercaptosuccinic acid induces calcium transients in cultured rhesus monkey kidney cells

Abstract

The maintenance of intracellular Ca 2+ homeostasis is critical to many cellular functions that rely on the calcium ion as a messenger. While attempting to characterize the effects of lead on intracellular calcium levels ([Ca 2+] i) in LLC-MK 2 Rhesus Monkey kidney cells, we observed that treatment with the metal chelating drug, meso-2,3-dimercaptosuccinic acid (DMSA) evoked transient increases in [Ca 2+] i. Changes in [Ca 2+] i were monitored using the Ca 2+ indicator dye Fura-2 and a dual wavelength fluorescence imaging system. In the presence of 2 mM extracellular Ca 2+, DMSA treatment caused a concentration-dependent (15–500 μM) transient increase in [Ca 2+] i returning to baseline levels within 30–60 s. Pharmacologic concentrations of DMSA (30 μM) stimulated a three-fold increase in [Ca 2+] i, which was spatiotemporally comparable to Ca 2+ transients induced by other calcium agonists. Depletion of inositol trisphosphate (IP 3)-sensitive [Ca 2+] i stores with the smooth endoplasmic reticulum calcium-ATPase (SERCA) inhibitor thapsigargin did not prevent DMSA-elicited increases in [Ca 2+] i, suggesting that Ca 2+ mobilized by DMSA was either extracellular or from an non-IP 3 releasable Ca 2+ pool. Treatment with glutathione, cysteine, or 2-mercaptoethanol caused similar but not identical calcium transients. Adenosine-5′-trisphosphate (ATP) also elicited transient increases in [Ca 2+] i similar to those of DMSA. No transient increases in [Ca 2+] i were elicited by DMSA or ATP in the absence of extracellular calcium. These data indicate that DMSA and other sulfhydryl compounds trigger an influx of extracellular calcium, suggesting a previously unobserved and unanticipated interaction between DMSA and the Ca 2+ messenger system.