EVIDENCE FOR A TSH-CONTROLLED ECTOPHOSPHOTYROSINE PHOSPHATASE IN PIG THYROID CULTURED-CELLS

In porcine thyroid cells in primary culture, thyrotropin (TSH) provoke s important morphological changes associated with specific thyroidal f unction recovery. TSH influences cell-cell interactions and follicular morphogenesis. In the present report, we identify an ectotyrosine pho sphatase activity controlled by chronic treatment with TSH. Specific s ubstrates and various inhibitors allowed us to characterize this activ ity. This tyrosine phosphatase is located at the outer surface of thyr oid cells as demonstrated by phosphotyrosylhistone hydrolysis. Control of cell viability and trypsin treatment confirm this extracellular lo calization. These data show that TSH activates ectotyrosine phosphatas e activity, suggesting a role for surface protein phosphorylation in r egulating specific functions of porcine thyroid cells in suspension. ( C) 1996 Academic Press, Inc.