RESUMO
This study explored whether sulforaphane changed basal [Ca²âº]i levels in suspended Madin-Darby canine kidney (MDCK) cells by using fura-2 as a Ca²âº-sensitive fluorescent dye. Sulforaphane at concentrations between 2.5-10 microM increased [Ca²âº]i in a concentration-dependent manner. This Ca²âº influx was inhibited by phospholipase A2 inhibitor aristolochic acid but not by Ca²âº channel blockers such as nifedipine, nimodipine, nicardipine, diltiazem, verapamil, econazole and SK&F96365. The Ca²âº signal was abolished by removing extracellular Ca²âº. In Ca²âº-free medium, pretreatment with sulforaphane did not alter the endoplasmic reticulum Ca²âº pump inhibitor thapsigargin-induced Ca²âº release suggesting sulforaphane did not induce slow Ca²âº release from endoplasmic reticulum. At concentrations between 1 and 20 microM, sulforaphane induced concentration-dependent decrease in cell viability which was not affected by pre-chelation of cytosolic Ca²âº with BAPTA/AM. Flow cytometry data suggest that 20 (but not 5 and 10) microM sulforaphane induced significant increase in sub G1 phase indicating involvement of apoptosis. Collectively, in MDCK cells, sulforaphane induced [Ca²âº]i rises by causing Ca²âº entry through phospholipase A2-sensitive pathways without inducing Ca²âº release from the endoplasmic reticulum. Sulforaphane also induced Ca²âº-independent cell death that might involve apoptosis.
