Polyploidy in mammalian urothelial cells.

The mitotic indices and the extent of polyploidy in urothelial cells of baboons, dogs and swine were studied. All three species had very low mitotic activity in vivo but short-term culturing of these cells in vitro stimulated mitosis thus enabling chromosome counts. Tetraploid cells were found in the urothelium of all three species, and higher ploidies also in dog and swine. There were substantial differences in the proportions of diploidy and higher ploidies among the three species and among individuals within each species. Dog urothelial cells were predominantly tetraploid (70%) while more swine cells were diploid (68%). Baboon urothelial cells had only two ploidy classes and 92% were diploid.