Effect of ACTH on Turnover of Phospholipids in Rat Adrenal Glands

Abstract

Time-course studies of 3H-choline incorporation into adrenal phospholipids revealed that the specific radioactivity reached to a maximum level at 9 hr after the isotope injection in untreated control animals, while in ACTH-treated animals, a maximum incorporation was already attained by 2 hr postinjection. The effect of ACTH on the incorporation was relatively prompt, the effect became evident as early as 1.5 hr after the treatment of animals. The rate of the incorporation in ACTH-treated animals was about twice that of the control. The incorporated radioactivity was decreased with the half-life of 2.9 days in phospholipids of control adrenals. On the other hand, the incorporated choline was well retained in adrenals of animals which receive daily treatment with ACTH throughout the experimental period of 7 days. The rate of phospholipid exchange between liver microsomes and adrenal mitochondria was not markedly influenced by treatment of animals with ACTH. Physiological implications of these observations were discussed.

ACTH stimulation on cholesterol side chain cleavage activity of adrenocortical mitochondria

“…Ichii et al(149) described that ACTH stimulated the incorporation of choline into phospholipid by adrenocortical postmitochondrial fractions. Ichii et al(149) described that ACTH stimulated the incorporation of choline into phospholipid by adrenocortical postmitochondrial fractions.…”

Effect of ACTH <I>in vivo</I> on the Phospholipid Exchange between Adrenal Microsomes and Mitochondria <I>in vitro</I>

“…The increased rate of 3H-choline incorporation into phospholipids of mitochondria as well as into microsomes was observed shortly after ACTH administration (Ichii, 1970, Ichii et al, 1971) and this might be attributable, at least in part, to the effect of ACTH on the rate of phospholipid exchange in mitochondria) membrane system in addition to on the biosynthetic system in microsomes. The i esponse of adrenal phospholipid to ACTH seems to be quite prompt and reached almost maximum level within a day after start of the treatment (Ichii et al, 1972), therefore, the low rate of phospholipid exchange observed in ACTH 3 days-mitochondria might possibly be explained by that the elevated rate of exchange has already taken place at early phase of ACTH-treatment. Increased phospholipid content in adrenal mitochondria) membranes 3 days after start of ACTH-treatment was detected (Ichii et al, 1972) and this might support the view mentioned above.…”

“…somes. A part of results of the preliminary experiment in which labeled liver microsomes were used as the donor of phospholipid has already been reported (Ichii et al, 1971). Blob et al(1971) presented evidences for the phospholipid exchange between inner and outer membranes of rat liver mitochondria in vivo.…”

“…In the previous reports from this laboratory (Ichii, 1970, Ichii et al, 1971, it was revealed. that administration of ACTH caused an increased 3H-choline incorporation into phospholipid fraction of rat adrenals and the rate of increase in the incorporation due to ACTH administration was most conspicuous in the inner membrane fraction of mitochondria.…”

“…In the present report, the effect of acutely and chronically administered ACTH on the rate of phospholipid exchange in vitro between rat adrenal microsomes and mitochondria will be described. (Ichii, 1970).…”