Cell kinetics of mouse urinary bladder epithelium. I. Circadian and age variations in cell proliferation and nuclear...

The urinary bladder epithelium contains nuclei with diploid, tetraploid and octoploid DNA content. A study in mice has been performed on mitotic activity, DNA synthesis and ploidy. The study has confirmed previous findings of an extremely low mitotic activity and a LI of 0.40 +/- 0.04%. The results indicate a higher DNA synthesis during the night as compared to the day. The relative numbers of diploid-, tetraploid- and octoploid cells have been estimated by micro-flow fluorometry. The mean values of these different classes were diploid: 39.40 +/- 1.4%, tetraploid: 53.27 +/- 1.00% and octoploid: 4.41 +/- 0.22%. Hexaploid DNA values with a mean of 2.51 +/- 0.13% were found and the significance of hexaploid pulses is discussed. The different ploidy classes changed during the neonatal period with a decrease of the diploid class and an increase of the tetraploid class. A reduction of the octoploid class about 4 weeks after birth was seen. The distribution of the different classes became stabilized around the second month.