Zn2+ increases resting cytosolic Ca2+ levels and abolishes capacitative Ca2+ entry induced by ATP in MDCK cells.
The effect of Zn2+ on Ca2+ signaling in Madin Darby canine kidney (MDCK) cells was investigated by measuring the changes in the fluorescence of the Ca2+-sensitive dye fura-2. Zn2+ significantly increased cytoplasmic free Ca2+ levels ([Ca2+]i) at concentrations of 2-100 microM. The maximum response was obtained at concentrations of 25-100 microM. The [Ca2+]i rise induced by 100 microM Zn2+ consisted of a gradual rise and a plateau phase, and was primarily mediated by La3+-sensitive extracellular Ca2+ influx because the [Ca2+]i rise was abolished by pretreatment with 100 microM La3+ or removal of extracellular Ca2+, and that Zn2+ induced Mn2+ quench of fura-2 fluorescence at 360 nm excitation wavelength which was prevented by pretreatment with 100 microM La3+. Pretreatment with 100 microM Zn2+ for 220 s did not reduce the [Ca2+]i rise induced by the endoplasmic reticulum (ER) Ca2+ pump inhibitor, thapsigargin, suggesting that Ca2+ release from the ER played a minor role in the Zn2+-induced [Ca2+]i rise. Zn2+ (100 microM) nearly abolished the capacitative Ca2+ entry induced by ATP (100 microM). We also investigated the effect of Zn2+ pretreatment on the [Ca2+]i rise induced by ATP. Zn2+ (100 microM) affected ATP-induced [Ca2+]i rise by abolishing capacitative Ca2+ entry and increasing [Ca2+]i on its own without altering Ca2+ release from intracellular sources. The effect of Zn2+ on [Ca2+]i was dissociated from changes in membrane potential.
Jan
C R
CR
Department of Medical Education and Research, Veterans General Hospital-Kaohsiung, Taiwan R.O.C. crjan@isca.vghks.gov.tw.
Wu
S N
SN
Tseng
C J
CJ
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002460:Cell Line; D002712:Chlorides / Q000494:pharmacology*; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects; D019284:Thapsigargin / Q000494:pharmacology; D017967:Zinc Compounds / Q000494:pharmacology*
D002712:Chlorides; D017967:Zinc Compounds; D019284:Thapsigargin; C016837:zinc chloride; D000255:Adenosine Triphosphate; D002118:Calcium