Effect of Corticotrophin on Protein and Phospholipid Metabolism in Subcellular Fractions of Adrenal Glands
1972 年 71 巻 4 号 p. 615-623
詳細
1972 年 71 巻 4 号 p. 615-623
1. Protein and phospholipid contents were determined in rat adrenal subcellular fractions during the course of tissue growth induced by successive administration of ACTH. Wet weight of the tissue was increased 5 times over that of the control, while increases in protein and phospholipid were 230 and 70% over the respective control after 10 days of the treatment. Proteins in the post-mitochondrial fraction and phospholids in the crude nuclear fraction showed a most profound increase.
2. Phospholipid responded to ACTH promptly and reached the almost maximum level within a day after start of the treatment, while the content of protein increased gradually during the experimental period.
3. Concentrations of plasma corticosterone in ACTH-administered animals was sus-tained at a high level and remained almost unchanged throughout the experimental period.
4. Simultaneous labeling of protein with 3H-leucine and of phospholipid with 3H-choline was performed to examine short-and long-term effects of ACTH on the biosynthesis of these compounds. At 3.5hr postinjection of ACTH, increased protein synthesis was observed only in the inner membrane and matrix fraction of mito-chondria, while, the rate of incorporation of 3H-choline into phospholipid was stim-ulated in every subcellular fractions. After 3 days of consecutive ACTH administra-tion, the rate of protein labeling was significantly elevated, while the rate of 3H-choline incorporation returned to the control level.
5. Phospholipid content was markedly increased in the outer membrane fraction of mitochondria but the increase in phospholipid of the other subcellular fractions were quite moderate at 3 days after the start of the treatment.
6. Half-life of protein and phospholipid in the adrenal was enlengthened by the administration of ACTH.
7. Administration of cycloheximide prior to ACTH injection abolished the effect of the hormone on the both corticosterone production and the rate of 3H-choline incorpo-ration into phospholipids of the adrenal. Similarities were obtained between responses of steroid hormone production and of phospholipid biosynthesis to ACTH and cyclo-heximide.
8. Physiological implications of these observations were discussed.
