Effect of TRH on 5’-Deiodinases in Rat Pituitary Glands
It is well known that the activity of 5’-deiodinase in the pituitary increases in thyroidectomized rats (1–4). However, the cause of this increase in the activity of 5’-deiodinase has not been elucidated. Either the direct effect of reduced thyroid hormones or the enhancement of the sensitivity to TRH was considered as the causative factor. Recently, it was reported that TRH increased the activity of 5’-deiodinase of cultured GH4C1 cells (5). Hypothalamic factors, including TRH, were also reported to regulate 5’-deiodinase activity in the pituitary (6). The modulation of 5’-deiodinase activity by trophic hormone per se was exemplified in the 5’-deiodinase of thyroid gland. It is increased by TSH, while that in liver and kidney was not influenced at all (7). From this evidence, it is conceivable that TRH stimulates the increase of 5’-deiodinase in pituitary in vivo. To determine the effect of TRH on pituitary T4 5’-deiodinase in vivo, the present experiments were carried out.
KeywordsChronic Treatment Deiodinase Activity Trophic Hormone Hypothalamic Factor GH4C1 Cell
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- 5.Koenig RJ. Program and Abstracts of the American Endocrine Society 845, 1985.Google Scholar