APOPTOSIS IN DOG THYROID-CELLS

Apoptosis, a physiological cell death, has been shown to be involved i n tissue homeostasis as well as in tissue regression due to hormone de privation. The thyroid cell population slowly turns over, with cell lo ss compensating mitogenicity. In the absence of thyrotropin, the cell population decreases. The possible involvement of apoptosis in this lo ss has been studied. We show in this report that deprivation of serum, epidermal growth factor and thyrotropin triggers internucleosomal DNA fragmentation and morphological modifications characteristic of apopt otic cell death in dog thyroid cells in primary culture; cycloheximide treatment has the same effect. This indicates that thyrocytes are end owed with a constitutive apoptosis ''program'' and that the latter mig ht be involved in the thyroid regression observed in vivo in the absen ce of full growth stimulation of the gland. (C) 1994 Academic Press, I nc.