Effect of hypoxia on secretion of ACTH in the rat

Abstract

Body weights, organ weights, and blood and pituitary ACTH concentrations were determined in rats exposed continuously to 20.9, 15.0, or 10.0% O2 atmospheres at normal barometric pressure for periods ranging from 3 to 120 hr. Hypoxia resulted in some loss of body weight, and loss of weight of the thymus and the ovary. The weight of the adrenals increased. Blood ACTH rose rapidly after exposure to hypoxic conditions, remaining elevated for the duration of the experiment. Control animals (20.9% O2) placed in the same chamber had detectable blood ACTH only at the 3-hr sampling time. Pituitary ACTH also rose rapidly during hypoxia, the elevation being greatest with the most severe hypoxic state. The rate of ACTH synthesis and secretion in the resting state and during the stress of hypoxia is discussed.

Prolonged Hypoxic Stress Increases Adrenal Cholesterol Reserve in Rats Without Causing Adrenal Hypertrophy

“…1 We noticed weight loss and haematocrit increase, 3 but not glandular hypertrophy, in rats after hypoxic stress for 3 weeks. Marks et al observed an increased adrenal weight in rats after hypoxic stress for 5 days.…”

“…Marks et al observed an increased adrenal weight in rats after hypoxic stress for 5 days. 1 We noticed weight loss and haematocrit increase, 3 but not glandular hypertrophy, in rats after hypoxic stress for 3 weeks. Perhaps, hypoxic stress of rats for more than 5 days may induce alternative adaptation mechanisms that could offset the trophic effect of ACTH.…”

“…cholesterol, conceivably resulting from increased circulating ACTH. 1,2 Whether these increases are associated with elevations of steroidogenic acute regulatory protein (StAR) and sterol carrier protein-2 (SCP2), two key factors of adrenal subcellular movement of cholesterol, 7 remains unknown.…”

“…1,2 The decrease in aldosterone synthesis has been theorized as a homeostatic mechanism to maintain potassium balance in the face of respiratory alkalosis induced by hyperventilation. The increase in corticosterone production has been associated with elevations of both pituitary adrenocorticotropic hormone (ACTH) concentration and circulating ACTH activity.…”

“…The increase in corticosterone production has been associated with elevations of both pituitary adrenocorticotropic hormone (ACTH) concentration and circulating ACTH activity. 1,2 The decrease in aldosterone synthesis has been theorized as a homeostatic mechanism to maintain potassium balance in the face of respiratory alkalosis induced by hyperventilation. 2 The present paper reports on effects of hypoxia on adrenal cholesterol reserve in the rat.…”