TY - JOUR
T1 - Daily variations in type II iodothyronine deiodinase activity in the rat brain as controlled by the biological clock
AU - Kalsbeek, A.
AU - Buijs, R.M.
AU - Van Schaik, R.
AU - Kaptein, E.
AU - Visser, T.J.
AU - Doulabi, B.Z.
AU - Fliers, E.
PY - 2005
Y1 - 2005
N2 - Type II deiodinase (D2) plays a key role in regulating thyroid hormone-dependent processes in, among others, the central nervous system (CNS) by accelerating the intracellular conversion of T-4 into active T-3. Just like the well-known daily rhythm of the hormones of the hypothalamo-pituitary-thyroid axis, D2 activity also appears to show daily variations. However, the mechanisms involved in generating these daily variations, especially in the CNS, are not known. Therefore, we decided to investigate the role the master biological clock, located in the hypothalamus, plays with respect to D2 activity in the rat CNS as well as the role of one of its main hormonal outputs, i.e. plasma corticosterone. D2 activity showed a significant daily rhythm in the pineal and pituitary gland as well as hypothalamic and cortical brain tissue, albeit with a different timing of its acrophase in the different tissues. Ablation of the biological clock abolished the daily variations of D2 activity in all four tissues studied. The main effect of the knockout of the suprachiasmatic nuclei (SCN) was a reduction of nocturnal peak levels in D2 activity. Moreover, contrary to previous observations in SCN-intact animals, in SCN-lesioned animals, the decreased levels of D2 activity are accompanied by decreased plasma levels of the thyroid hormones, suggesting that the SCN separately stimulates D2 activity as well as the hypothalamo-pituitary-thyroid axis
AB - Type II deiodinase (D2) plays a key role in regulating thyroid hormone-dependent processes in, among others, the central nervous system (CNS) by accelerating the intracellular conversion of T-4 into active T-3. Just like the well-known daily rhythm of the hormones of the hypothalamo-pituitary-thyroid axis, D2 activity also appears to show daily variations. However, the mechanisms involved in generating these daily variations, especially in the CNS, are not known. Therefore, we decided to investigate the role the master biological clock, located in the hypothalamus, plays with respect to D2 activity in the rat CNS as well as the role of one of its main hormonal outputs, i.e. plasma corticosterone. D2 activity showed a significant daily rhythm in the pineal and pituitary gland as well as hypothalamic and cortical brain tissue, albeit with a different timing of its acrophase in the different tissues. Ablation of the biological clock abolished the daily variations of D2 activity in all four tissues studied. The main effect of the knockout of the suprachiasmatic nuclei (SCN) was a reduction of nocturnal peak levels in D2 activity. Moreover, contrary to previous observations in SCN-intact animals, in SCN-lesioned animals, the decreased levels of D2 activity are accompanied by decreased plasma levels of the thyroid hormones, suggesting that the SCN separately stimulates D2 activity as well as the hypothalamo-pituitary-thyroid axis
UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-14244265221&partnerID=MN8TOARS
U2 - https://doi.org/10.1210/en.2004-0763
DO - https://doi.org/10.1210/en.2004-0763
M3 - Article
C2 - 15550511
SN - 0013-7227
VL - 146
SP - 1418
EP - 1427
JO - Endocrinology
JF - Endocrinology
IS - 3
ER -