The pituitary–thyroid axis during the parr–smolt transformation of Coho salmon, Oncorhynchus kisutch: Quantification of TSH β mRNA, TSH, and thyroid hormones

The objective of this investigation was to quantify pituitary thyroid stimulating hormone β mRNA, pituitary and plasma TSH and plasma thyroid hormone levels during the parr–smolt transformation of Coho salmon that occurs in spring from February to May

Donald A. Larsen; Penny Swanson; Walton W. Dickhoff

2011

Scholarcy highlights

  • The objective of this investigation was to quantify pituitary thyroid stimulating hormone β mRNA, pituitary and plasma TSH and plasma thyroid hormone levels during the parr–smolt transformation of Coho salmon that occurs in spring from February to May
  • The status of the pituitary–thyroid axis was assessed using an RNase protection assay for pituitary TSH β mRNA and radioimmunoassays for salmon pituitary and plasma TSH and thyroid hormones
  • TSH β mRNA was highest during late winter and gradually declined during spring
  • The increased thyroid sensitivity to TSH, in the face of relatively constant plasma TSH levels, may be the major factor responsible for the increased thyroid activity observed during smoltification
  • ► The first quantification of TSH protein levels during smolting using RIA. ► During smoltification, pituitary and plasma TSH levels remain relatively stable. ► TSH beta levels increase before declining with the surge in thyroid hormones. ► Results support both the peripheral control and aspects of the central control model for thyroid regulation in teleosts

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