副腎不全における血中corticotrophin量とcorticotrophinの合成及び放出
スポンサーリンク
概要
- 論文の詳細を見る
A series of experiments were performed to study the influence of exogenous ACTH-administration on the release of endogenous corticotrophin or its synthesis in the pituitary glands of bilaterally adrenalectomized Wistar rats.<BR>The first set of experiments was made to see whether surgical hypophysectomy of the rat, that had conventionally been used in the adrenal ascorbic acid depletion test for the corticotrophin assay, could be substituted by the administration of a large dose of dexamethasone which sufficiently inhibits the release of corticotrophin.<BR>1) The maximum depletion of adrenal ascorbic acid was observed about 60 minutes after the intravenous administration of ACTH in hypophysectomized rats.<BR>2) The discharge of corticotrophin due to stress of unilateral adrenalectomy in non-hypophysectomized rats was completely blocked by an administration of 0.5 mg. or more dexamethasone-21-phosphate disodium, 3 to 5 hours prior to surgery.<BR>3) The responsiveness of the non-hypophysectomized rats treated with 1 mg. dexamethasone 4 hours prior to the intravenous injection of 'Armour' ACTH in varying doses was found to be linear from 0.25 to 2.0 mU. of ACTH, on the basis of determination of the adrenal ascorbic acid depletion. The dose-response curve was expressed by the equation Y= 98.5 log X + 97.5. (Y : the reduction of adrenal ascorbic acid in mg. per 100 gm. of the tissue. X : the dose in mU. of ACTH per 100 gm. of body weight. the index of precision (λ) being 0.215.) <BR>Since the equation showed that the dexamethasone-treated rats were quite sensitive enough to ACTH to facilitate a quantitative assay of corticotrophin, this procedure has routinely been uesd in our laboratory.<BR>4) The amount of pituitary corticotrophin in the adrenalectomized rats increased following an administration of ACTH for 6 days, and this increase appeared to depend on the dose of administered ACTH-Z.<BR>5) Ten minutes after the stress due to shamadrenalectomy, the amount of pituitary corticotrophin in the adrenalectomized rats treated with various doses of ACTH-Z decreased significantly. The greater fall occurred in the group of rats which had been given a higher dose of ACTH-Z and known to contain a larger amount of pituitary corticotrophin.<BR>6) The increase in the pituitary corticotrophin concentration following an administration of ACTH-Z for 6 days in the adrenalectomized rats could be partially inhibited by a simultaneous administration of dexamethasone with ACTH-Z. However, the amount of pituitary corticotrophin in the rats so treated was more than that in the rats treated with dexamethasone alone.<BR>7) The blood of adrenalectomized and saline-treated rats showed no detectable corticotrophic activity. On the other hand, adrenalectomized and ACTH-Z plus dexa-methasone-treated rats showed a significant increase of the adrenalectomized and ACTH-Z-traeted rats.<BR>8) The degree of increase in the corticotrophin level of the blood by a stress depended on the resting level of corticotrophin in the pituitary gland. In both adrenalectomized, saline-treated and adrenalectomized, ACTH-Z-treated rats, however, the pituitary corticotrophin level recovered to the level in the non-stressed control rats within 24 hours after a stress.<BR>9) There was no significant difference in the pituitary corticotrophin level between the adrenalectomized non-stressed rats and the adrenalectomized repeatedly stressed ones which maintained a high level of circulating corticotrophin.<BR>The adminitration of non-physiologically large doses of long-acting ACTH for 6 days brought about not only a rise in the blood level of corticotrophin but slao a significant rise in the pituitary corticotrophin level in the adrenalectomized rats.
- 一般社団法人 日本内分泌学会の論文