Lack of thyroglobulin synthesis as an indicator of early random dedifferentiation of the Fischer rat thyroid cell line FRTL-5

Abstract

Fischer rat thyroid cells (FRTL-5) are widely used for the study of thyroid cell function. With age or transformation the characteristics of FRTL-5 cells change, leading to poor differentiation and accelerated growth. Thyroglobulin production from FRTL-5 cells indicates differentiation to a higher extent than does the cyclic adenosine-3',5'-monophosphate (cAMP) response to thyrotropin (TSH) and growth. This study investigated the release of the differentiation marker thyroglobulin from FRTL-5 cells into the medium during various early subcultures compared with cAMP response and cell growth. Growth was measured by ³H-thymidine incorporation into DNA and by the amount of DNA in each well. Cell differentiation was measured by release of cAMP and thyroglobulin from the cells. TSH (1 U/l) stimulated ³