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

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.