Frequency Spectrum of Transepithelial Potential Difference Reveals Transport-Related Oscillations

MONTALBETTI, N.; FISCHBARG J.

Cordoba

Congreso; XXXVIII reunión anual, Sociedad Argentina de Biofísica; 2009

How epithelia transport fluid is a fundamental issue that is unresolved. On the basis of experimental and theoretical work done on corneal endothelium, a fluid transporting epithelium, we suggest electro-osmotic coupling at the level of the intercellular junctions driven by the transendothelial electrical potential difference (TEPD) as the explanation of paracellular fluid transport. We collect frequency spectra of this potential difference in real-time. For what we believe is the first time for any epithelium, we report that, unexpectedly, the potential difference displays oscillations at many characteristic frequencies. The cellular activity of the corneal endothelium includes periodic processes manifested in the frequency range between ~ 0.1- 20 Hz. The TEPD frequency spectrum shows peaks with significant amplitudes in the frequency region below 2 Hz and a plateau where peaks are observed with reduced amplitude from ~ 2 Hz up to ~ 8 Hz. We also show that upon both stimulating cell activity and inhibiting ion transport mechanisms, there are corresponding changes in the oscillations amplitudes that mirror changes previously known for rates of fluid transport.  We conclude that several cotransporters and channels contribute to generate the TEPD operating each at characteristic frequencies, and that the largest contribution to TEPD comes from electrogenic sodium-bicarbonate cotransporters