I did transport experiments across Caco-2 cell monolayers for 2 periods within 5 hours (2.5 h of each period). With transport of the same substance different period of experiment, Papp increased. Do you have any idea about possible reason of this increment in Papp?
Dear Fali, this is quite common. Exchange of solutions, sampling and stirring gradually decreases junctional resistance, and thus causes increase in Papp (I take it that you Papp refers to the permeability of a paracellular marker?) We normally only make one exp. and seldom perform experiments longer than 3 hours max. Cells may recover somewhat though, if left unstirred and "unsampled" but this effect is highest in culture media and may not be significant in experimental buffers.
Thank you for both advices. My test substance is not interfere the integrity of the cell monolayers. However, the Papp was shooting 2-5 fold at the end of second period of the experiment (2.5-5 h) compared to the first period (0-2.5 h). It's quite big difference though. . .I just used HBSS/HEPES as a transport buffer and did not detect any change in TEER values. Is it possible that equilibration time (with only transport buffer) in between those 2 periods also affect this?
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