Cell division in the vomeronasal organ of the adult mouse.

Using [3H]thymidine labelling we could demonstrate the presence of a population of dividing cells in the vomeronasal neurosensory epithelium of the adult mouse. These cells are localised in the regions of the epithelium adjacent to its boundaries with the ciliated respiratory epithelium. With increasing survival times after thymidine administration, the labelled cells become situated progressively further away from the boundary region. The cluster of cells with labelled nuclei forms a loose column, consisting of labelled receptor cells, but in addition the immediately overlying supporting cell nuclei are also labelled. By 56 days after thymidine administration the cluster of labelled cells is separated from the epithelial boundary by a distance equivalent to about one-fifth of the total width of the epithelial sheet. There is little further change in position at 102 days. It is not clear to what extent this represents a turnover process as opposed to a continuing growth of the epithelium by accretion at the edges.