L. Wojnowski et al., CELL-TRANSFORMATION INDUCES A CYTOPLASMIC CA2-DARBY CANINE KIDNEY-CELLS( OSCILLATOR IN MADIN), Pflugers Archiv, 426(1-2), 1994, pp. 89-94
Alkaline stress transforms Madin-Darby canine kidney (MDCK) cells as i
ndicated by loss of epithelial structure, multilayer cell growth and f
ormation of foci. In the present study we report that transformed MDCK
cells (MDCK-F cells) exhibit spontaneous and lasting oscillations of
intracellular Ca2+ concentration ([Ca2+](i)), which are absent in non-
transformed cells. Oscillations, as revealed by Fura-2 video imaging,
were due to the activity of an inositol 1,4,5-trisphosphate-(InsP(3))-
sensitive Ca2+ store since their frequency was dependent on bradykinin
concentration and they were abolished by the phosphoinositidase C inh
ibitor U73122. Moreover, blockers of the cytoplasmic Ca2+-ATPase, thap
sigargin and 2,5-di-(tetr-butyl)-1,4-benzohydroquinone inhibited oscil
latory activity. In contrast, neither injection of ruthenium red, ryan
odine nor caffeine had any effect on oscillations. Analysis of the spa
tial distribution of [Ca2+](i) showed that Ca2+ transients originated
from an initiation site constant for a given cell and spread through t
he cell as an advancing Ca2+ wave. Oscillations started in a random ma
nner from single cells and spread over neighbouring cells, suggesting
a kind of intercellular communication. We conclude that MDCK-F cells h
ave acquired the ability for endogenous Ca2+ release through transform
ation. Oscillations are primarily due to the activity of an InsP(3)-se
nsitive cytosolic Ca2+ oscillator.