ラットの甲状線組織及び甲状腺内沃化アミノ酸分劃に及ぼす副腎皮質ホルモンの影響
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This report attempts to study the effect of adrenocortical steroids on the thyroid gland. 1) The effect of adrenocortical steroids (dexamethasone : 0.125 mg./100 gm. body wt., hydrocortisone : 5 mg./100 gm. body wt.) and ACTH (ACTH-Z : 3 I.U./100 gm. body wt.) on the thyroid gland in a rat, was studied.<BR>2) Wister male rats weighing 110 to 150 gm. were maintained on a standard diet, and iodine solution (9.6, μg. /day) was injected throughout the experiment.<BR>A tracer dose of 10 μc. of radioiodine was administered subcutaneously and 24 hrs. later, thyroidal radioactivity was measured once a day using a collimated scintillation counter over the thyroid gland. Radioactivity was corrected for physiological decay and the rate of the I<SUP>131</SUP> release was calculated by the method of least squares.<BR>Following the determination of the rate of the I<SUP>131</SUP> release in a control period, adrenocortical steroids (subcutaneously twice a day) or ACTH (intra muscularlly once a day) was administered and the rate of the release was compared with that in a control period.<BR>3) The mean rate (-λ) calculated of the thyroidal I<SUP>131</SUP> release in a control group was 0.262/ day and a daily injection of dexamethasone or ACTH induced a decrease of the rate while that of hydrocortisone an increase of the rate in two out of three rats.<BR>4) Then, saline solution or hydrocortisone to a control group was injected for 16 days and dexamethasone or ACTH injected for 18 days in subsequent experiments.<BR>The thyroid was weighed and a chromatogram was developed in BAW and BDA solvent after termination of the enzymic hydrolysis. Autoradiography was performed and radioactivity of each fraction was measured by a well-type scintillation counter.<BR>5) The mean thyroid weight was 8.2 mg/100 gm. body wt, in a control group and the weight increased in a dexamethasone and ACTH group. The mean values of serum total iodine revealed 6.8 μg./dl. and those of serum PBI 4.5 μg./dl. in a control group, and these values were not affected by the treatment with dexamethasone, hydrocortisone or ACTH. The weight ratio of iodine, 3-monoiodotyrosine (MIT), 3, 5-diiodotyrosine (DIT), 3, 5, 3',-triiodothyronine (T<SUB>3</SUB>) and thyroxine (T<SUB>3</SUB>) to all iodinated materials in the thyroid gland were 1.8%, 41.8%, 48.3%, 1.8% and 6.2%, respectively, in a control group.<BR>Dexamethasone decreased the ratio of T<SUB>3</SUB> + T<SUB>4</SUB>/MIT+ DIT and hydrocortisone increased the ratio of MIT/DIT and decreased T<SUB>3</SUB> + T<SUB>4</SUB>/MIT + DIT.<BR>6) On histological examination, the mean acinar cell hight was 8.3μ, e2 and the mean diameter of follicles was 35.4μ in a control group. The mean acinar cell height increased in the dexamethasone or hydrocortisone group and decreased in an ACTH group. The mean diameter of follicles decreased in the hydrocortisone group.<BR>7) These findings suggest that ACTH suppresses the thyroid functions but the effect of dexamethasone or hydrocortisone on the thyroid functions is a little different from that of ACTH. Moreover, it is likely that although dexamethasone and hydrocortisone may suppress either TSH secretion or action, they have also some effects on the level of the thyroid gland.
- 日本内分泌学会の論文