Acute lead (Pb 2+ ) exposure increases calcium oxalate crystallization in the inner medullary collecting duct, and is ameliorated by Ca 2+ /Mg 2+ -ATPase inhibition, as well as Capa receptor and SPoCk C knockdown in a Drosophila melanogaster model of nephrolithiasis.

Calcium oxalate (CaOx) kidney stones accumulate within the renal tubule due to high concentrations of insoluble deposits in the urine. Pb 2+ -induced Ca 2+ mobilization along with Pb 2+ -induced nephrotoxic effects within the proximal tubule have been well established; however, Pb 2+ mediated effects within the collecting duct remains insufficiently studied. Thus in vitro and ex vivo model systems were treated with increasing concentrations of lead (II) acetate (PbAc) ± sodium oxalate (Na 2 C 2 O 4 ) for 1 h, both individually and in combination. Pb 2+ -mediated solution turbidity increased 2 to 5 times greater post-exposure to 75, 100 and 200 μM Pb 2+ with the additional co-treatment of 10 mM oxalate in mouse inner medullary collecting duct (mIMCD-3) cells. Additionally, 100 μM and 200 μM Pb 2+ alone induced significant levels of intracellular Ca 2+ release. To validate Pb 2+ -mediated effects on the formation of CaOx crystals, alizarin red staining confirmed the presence of CaOx crystallization. Pb 2+ -induced intracellular Ca 2+ was also observed ex vivo in fly Malpighian tubules with significant increases in CaOx crystal formation via Pb 2+ -induced intracellular Ca 2+ release significantly increasing the average crystal number, size, and total area of crystal formation, which was ameliorated by tissue-specific SPoCk C transporter and Capa receptor knockdown. These studies demonstrate Pb 2+ -induced Ca 2+ release likely increases the formation of CaOx crystals, which is modulated by a G q -linked mechanism with concurrent Ca 2+ extracellular mobilization.