ACTH and brain RNA: changes in content and labelling of RNA in rat brain stem

The influence of synthetic ACTH1-24 and ACTH1-10 on rat brain RNA was studied. ACTH1-24 (5 IU/100 g s.c.) treatment resulted in a small decrease in labelling of brain stem RNA (-12%), measured 30 min after the injection of [5-3H] uridine (100 muCi; s.c.), without affecting the distribution of radioactivity of the acid-soluble precursor pool. Furthermore, a small and transitional reduction of total brain stem RNA was found. Similar treatment of adrenalectomized rats (36 h after surgery) resulted in a marked increase (+ 40%) in labelling of brain stem RNA, without affecting the distribution of radioactivity in the acid-soluble pool. In both intact and adrenalectomized rats, treatment with ACTH1-24 did not affect RNA of cortex cerebrum and cerebellum. ACTH1-10, a fragment of ACTH without corticotropic activity in vivo, exhibited no effect on brain stem RNA in either intact or adrenalectomized rats, nor did corticosterone (1 mg/100 g) affect adrenalectomized rats.