Apical cell damaged

Cell monolayers grown on Transwell filters have to be washed twice with freshly prepared and prewarmed HBSS. To avoid damage of the monolayer by hydrostatic pressure, first the medium from the basolateral compartment and then from the apical compartment has to be removed. The apical compartment is filled with 500 iL of fresh buffer and then the basolateral compartment with a volume of 1500 pL. 

Toxicants that reduce ATP disrupt cell volume, ion concentrations, and cell polarity. Disruption of cell volume and ion homeostasis occurs by toxicant interaction with the plasma membrane increasing ion permeability or by attenuahng energy produchon. ATP depletion results in a decrease in Na, K -ATPase activity, resulting in cell swelling, and ultimately cell rupture [54, 55]. The tubular epithelia are polarized cells with specific transporters on the apical and basolateral domains. When a toxicant causes ATP depletion there is a dissociation of the Na, K -ATPase from the actin cytoskeleton and a redistribution from the basolateral to apical domain in the renal proximal tubule cells [56]. The loss of polarity of the cells disrupts the adhesion complexes and loss of cell-to-cell contact that facilitates further renal damage. 

In LLC-PKj cells gentamicin induces membrane damage as shown by the loss of specific membrane enzymes (y-glutamyl transpeptidase, alkaline phosphatase and aminopeptidase), a decrease of the lysosomal enzyme N-acetyl-P-D-glucosaminidase, an inhibition of apical Na -dependent glucose transporter and the basolateral Na-K-ATPase pump as well as a decrease in dome formation [141, 142]. Furthermore gentamicin results in a dose dependent decrease in intracellular ATP and cAMP [142]. 

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