Microgravity effects on tsh stimulation of differentiated thyroid cultured cells FRTL5

Thyrotropin induces biochemical and morphological changes in cultures of the normal rat thyroid cell strain FRTL5. To ascertain if microgravity conditions may change hormonal responses at subcellular and molecular levels, a possible explanation for the many pathophysiological changes occurring in astronauts during space missions, we performed: I) simulated microgravity experiments in clinostat and II) one true microgravity experiment of short duration (6 min.) in the CIS-5 module in the MASER-7 parabolic fight using FRTL5 cells. I) In clinostat, in vitro cellular responses (cyclic-AMP production) following Thyrotropin stimulation was enhanced during acute exposure to simulated microgravity. II) In flight Thyrotropin-stimulated cAMP production, although very low, was reduced in microgravity in comparison to on-ground lxg controls. Also cytoskeleton reorganization was significantly different from on-ground controls: after 6 minutes of microgravity, unstimulated cells appeared partially stimulated, whereas approximately 50% of the Thyrotropin-stimulated cells appeared instead unstimulated.