Response to thyrotropin of normal thyroid follicular cell strain FRTL5 in hypergravity

Thyroid hormones control every cell in the organisms and, as indicated by m any hormonal changes in astronauts during and shortly after space missions, its complex regulation may be influenced by gravity. To test in vitro the effects of gravity environment on thyroid, we selected a unique cultured ce ll system: the FRTL5, a normal follicular thyroid cell strain in continuous culture, originally derived from adult rat thyroids. To establish if modif ications of the gravitational environment may interfere with post-receptori al signal transduction mechanisms in normal mammalian cultured cells, follo wing our previous microgravity experiments, we exposed thyrotropin-stimulat ed and unstimulated FRTL5 cells to hypergravity (5 g and 9 g) in a special low-speed centrifuge. At all thyrotropin doses tested, we found significant increases in terms of cyclic AMP production in FRTL5 thyroid cells. The da ta here reported correlate well with our previous microgravity data, showin g that the FRTL5 cells functionally respond to the variable gravity force i n a dose-dependent manner in terms of cAMP production following TSH-stimula tion. (C) Societe francaise de biochimie et biologie moleculaire / Elsevier , Paris.