The involvement of thyroid hormones and cortisol in the osmotic acclimation of Solea senegalensis

The present findings demonstrate that the thyroid sys­ tem, viz. the systemic free T4 concentrations and outer ring deiodination activi­ ties in peripheral tissues, and the hypothalamo-pituitaryinterrenal axis in S. senegalensis are responsive to changes in environmental salinity

F.J. Arjona; L. Vargas-Chacoff; M.P. Martín del Río; G. Flik; J.M. Mancera; P.H.M. Klaren

2007

Scholarcy highlights

  • The main end product from the hypothalamo-pituitarythyroid axis is the prohormone thyroxine
  • The present findings demonstrate that the thyroid sys­ tem, viz. the systemic free T4 concentrations and outer ring deiodination activi­ ties in peripheral tissues, and the hypothalamo-pituitaryinterrenal axis in S. senegalensis are responsive to changes in environmental salinity
  • The negative correlation between plasma cortisol and plasma fT4 levels indicates an interaction between cortisol and the thyroid system
  • The increased hepatic and renal ORD activities observed on day 1 post-transfer are consistent with the decreased plasma fT4 levels measured at that time point, and coincide with abrupt changes in plasma osmolality
  • Our data suggest that the concerted actions of the thyroid system and cortisol are involved in the short-term salinity adaptation of S. senegalensis
  • In our time-course study, the chronology of changes in plasma parameters, together with the changes in hepatic and renal 0 R D activities allows two phases to be distinguished in S. senegalensis: an initial adjust­ ment period, ending on day 3 post-transfer after which plasma osmolalities, fT4 and cortisol levels and peripheral ORD activities return to basal values; followed by a chronic regulatory period with sustained changes in bran­ chial Na+,K+-ATPase activities
  • Other peripheral enzyme activities other than 5'-deiodinases that catalyze outer ring deiodination are responsive to changes in environmental salinity and could cause or contribute to the changes in plasma free T4 levels observed in this experiment

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