Proliferating hair cell precursors in the ear of a postembryonic fish are replaced after elimination by cytosine arabinoside

Identified, proliferating S-phase cells in the postembryonic fish ear are known to be the precursors to new hair cells. It is not known, however, whether the ability to proliferate is restricted to a small population of cells. The ability of cells that are not normally in the cell cycle to enter S-phase was examined using the antimitotic drug cytosine arabinoside (ara-C). The normal population of S-phase cells in the saccule was destroyed by a single large dose of ara-C. Two weeks later, the prsence of S-phase cells was evaluated using the S-phase marker bromodeoxyuridine. The results strikingly demonstrate that S-phase cells are replaced, since S-phase cells returned to the saccule in the same number as found in normal fish. The data are interpreted to suggest that a large number of nonsensory support cells are capable of entering the cell cycle and that some mechanism must regulate which of these are actually cycling at any given time. © 1995 John Wiley & Sons, Inc.