Assessment and validation of a microinjection method for kinetic analysis of [Ca2+]i in individual cells undergoing apoptosis.
Normal and malignant epithelial cells are induced to undergo apoptosis by a large variety of mechanistically diverse agents. Regardless of inducing agent, apoptosis characteristically occurs asynchronously within a population of epithelial cells over a period of 12-96 h and is associated with permeability and enzymatic perturbations. Pre-loading of cells with acetoxymethyl esters (AM) derivatives of fluorescent Ca2+ indicators (i.e. fura-2, indo-1, fluo-3) by passive diffusion allows longitudinal kinetic analysis of acute [Ca2+] changes subsequent to exposure to apoptosis inducing agents. Using prostate cancer cell lines, however, it is demonstrated that dye leakage and compartmentalization into organelles limit such passive loading to longitudinal [Ca2+]i measurements of < 2 h. Post-loading of cells exposed to the apoptosis inducing agent for several hours is also inaccurate owing to decreased loading efficiency and de-esterification of the probes resulting in increased production of fluorescent Ca(2+)-insensitive dye species. To accurately measure kinetics of [Ca2+]i changes longitudinally in individual cells undergoing apoptosis, cells were microinjected with fura dextran and maintained in a physiologic environment. [Ca2+] and morphological changes characteristic of apoptosis were then followed simultaneously in individual cells over several days following exposure to the apoptosis inducing agent.
Tombal
B
B
John Hopkins Oncology Center, Baltimore, MD 21231, USA.
Denmeade
S R
SR
Isaacs
J T
JT
D000818:Animals; D017209:Apoptosis; D002118:Calcium / Q000378:metabolism*; D005456:Fluorescent Dyes; D016257:Fura-2; D006801:Humans; D007700:Kinetics; D008845:Microinjections / Q000379:methods*; D051381:Rats; D013997:Time Factors; D014407:Tumor Cells, Cultured
D005456:Fluorescent Dyes; D002118:Calcium; D016257:Fura-2