Transfer function between calcium flux and fluorescence signal

ALEJANDRA C VENTURA; IAN PARKER; SILVINA PONCE DAWSON

Buenos Aires, Argentina

Congreso; XIV International Biophysics Congress; 2002

The Biophysical Society

The liberation of calcium ions from the endoplasmatic reticulum into the cytosol through inositol triphosphate receptor/channels (IP3R) plays a central role in regulating numerous forms of cellular activity. A difficulty in deriving quantitative information from Ca2+ images regarding the magnitude and kinetics of the underlying Ca2+ fluxes, arises because the fluorescence signal represents an integral of Ca2+ release over the finite volume of the focal spot and is influenced by factors including dye and Ca2+ diffusion and Ca2+ binding kinetics. We are proposing a dual, tightly integrated approach of mathematical modeling and high resolution cellular calcium imaging to derive a transfer function between Ca2+ flux and flluorescence signal. The key experiment that we are modeling is the ionophoretically injection of Ca2+ ions into the cell. The motivation is, then, to compare the resulting signal to one observe during the release from the IP3R. Experimentally, it is impossible to know the Ca2+ current that is injected, so we developed a model which provides an analyitic solution, and, therefore, allows an easy comparison with experiments. We also evaluated the validity of the approximations involved.