Prostaglandinsのラット甲状腺内ホルモン合成及び血漿TSHに及ぼす刺激効果

抄録

It is now postulated that prostaglandins (PG) are widely distributed in mammalian tissues and stimulate adenyl cyclase-cyclic AMP system in various organs. The present study was undertaken in an attempt to clarify the effect of PG on pituitary-thyroid axis in vivo.
Rats were maintained on a low-iodine diet for 8 days. The animals received graded doses (10-500 μg) of PGE₁, PGE₂ and PGF_2α ip daily from day 5 to the day of autopsy. The 4-hr thyroid ¹³¹I uptake was consistently higher in 10 μg PGE₁, 10 μg PGE₂ and 100 μg PGF_2α-treated rats than in the controls. Higher T₃/T₄ ratios were found in the diagested thyroids of PG-treated rats. Serum T₄ levels appeared to be increased by the PG administration. However, a single injection of PG did not affect thyroid ¹³¹I uptake in iodine-deficient animals. No change in the thyroid ¹³¹I uptake was found in iodinereplete rats chronically treated with PG. The increase in plasma TSH levels during treatment with 30 μg PGE₁ and PGE₂ was clearly shown. A similar result was also obtained with 100 μg PGF_2α.
The increase in thyroid ¹³¹I metabolism produced by the repeated administration of PG in iodine-deficient rats is due presumably to the direct stimulation on the thyroids of rats. In addition, PG elevated plasma TSH levels in such animals, probably mediated through the hypothalamic-pituitary system.