CELL-CYCLE OF GLOBOSE BASAL CELLS IN RAT OLFACTORY EPITHELIUM

The olfactory epithelium of adult mammals has the unique property of g enerating olfactory sensory neurons throughout life. Cells of the basa l compartment, which include horizontal and globose basal cells, are r esponsible for the ongoing process of neurogenesis in this system. We report here that the globose basal cells in olfactory epithelium of ra ts, as in mice, are the predominant type of proliferating cell, and ac count for 97.6% of the actively dividing cells in the basal compartmen t of the normal epithelium. Globose basal cells have not been fully ch aracterized in terms of their proliferative properties, and the dynami c aspects of neurogenesis are not well understood. As a consequence, i t is uncertain whether cell kinetic properties are under any regulatio n that could affect the rate of neurogenesis. To address this gap in o ur knowledge, we have determined the duration of both the synthesis ph ase (S-phase) and the full cell cycle of globose basal cells in adult rats. The duration of the S-phase was found to be 9 hr in experiments utilizing sequential injections of either IdU followed by BrdU or H-3- thy followed by BrdU. The duration of the cell cycle was determined by varying the time interval between the injections of H-3-thy and BrdU and tracking the set of cells that exit S shortly after the first inje ction. With this paradigm, the interval required for these cells to tr averse G2, M, G1, and a second S-phase, is equivalent to the duration of one mitotic cycle and equals 17 hr. These observations serve as the foundation to assess whether the cell cycle duration is subject to re gulation in response to experimental injury, and whether such regulati on is partly responsible for changes in the rate of neurogenesis in su ch settings. (C) 1995 Wiley-Liss, Inc.