Physical Geography and Sciences


Kalina Rice



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Kalina Rice, BIO 498: Honors Research
Faculty Mentors: Professor Derek Beahm, Biology and Professor Stephen Thompson, Biology

Cells actively regulate their volume to maintain normal function. Osmotic challenges will cause net water movement across the plasma membrane such that cells swell in hypotonic solutions and shrink in hypertonic solutions. Cells respond to volume changes by activating different channels and transporters to move ions and small molecules across the membrane to restore normal volume. We show that cell swelling under reduced external calcium conditions increases the membrane permeability to a small fluorescent molecule, Lucifer Yellow, in Normal Rat Kidney (NRK) cells. Fluorescence microscopy was used to show that Lucifer Yellow is excluded by cells in normal isotonic conditions but enters cells in hypotonic solutions. This swelling induced dye uptake is shown to be calcium sensitive, and only occurs under reduced external calcium levels. There are several different types of channels that could account for the transfer of Lucifer Yellow, including connexin and pannexin hemichannels formed by gap junction proteins and/or volume-regulated anion channels (VRACs). A pharmacological approach was used to help identify the channel by assaying dye uptake in the absence or presence of drugs known to block certain classes of channels. Preliminary data shows that probenecid, a drug thought to be effective in blocking pannexin channels but not connexin channels, did not block dye uptake whereas drugs used to block hemichannels, such as carbenoxolone and oleamide, do block the dye uptake. However, these drugs may also affect VRACs and so further testing using a larger panel of drugs will be needed to help identify the channel responsible for swelling-induced dye uptake in NRK cells.

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Swelling Induced Dye Uptake in Normal Rat Kidney Cells
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