PtK2 is a marsupial epithelial cell line that was initiated from adult male rat kangaroo (Potorous tridactylus) kidney tissue. The rat kangaroo, or potoroo, is a long-nosed, nocturnal native of Australia and Tasmania with omnivorous feeding habits. Prior to the establishment of the PtK2 line, another line of cells was developed from a female rat kangaroo. Dubbed PtK1, that line was the first permanent marsupial cell line ever developed. Both PtK2 and PtK1 cells have been utilized in a variety of research projects, but are especially useful in studies of mitosis.

Testing indicates that the PtK2 cell line demonstrates susceptibility to a number of different viruses, including herpes simplex, vaccinia, coxsackievirus A9, and vesicular stomatitis (Ogden strain). Poliovirus 2, adenovirus 5, and coxsackievirus B5 are among the viruses to which the cells have proven to be resistant. PtK2 epithelial cells stain positive for the intermediate filament protein keratin and are negative for the enzyme reverse transcriptase. Similar to other epithelial cells, cultured PtK2 cells exhibit significant contact inhibition to migration, tending to form close bonds with one another and forming sheets similar to the epithelial sheets that occur naturally in the body.

The adherent log phase culture of PtK2 cells illustrated above was treated for one hour with MitoTracker Red CMXRos in order to label the mitochondrial network, and the fixed cells were then incubated with mouse anti-cytokeratin primary antibodies followed by goat anti-mouse secondary antibodies (IgG) conjugated to Cy2. The nuclei were counterstained with DAPI. Images were recorded in grayscale with a 12-bit digital camera coupled to a Nikon Eclipse 80i microscope equipped with bandpass emission fluorescence filter optical blocks. During the processing stage, individual image channels were pseudocolored with RGB values corresponding to each of the fluorophore emission spectral profiles.