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.