Acute and chronic effects of ACTH on thermogenesis and brown adipose tissue in the rat.

A single injection of ACTH stimulated metabolic rate in the rat, and this effect was enhanced in hyperphagic cafeteria-fed rats. Chronic treatment with ACTH significantly reduced body weight, energy gain and energetic efficiency in stock-fed rats. Thermogenic responses to noradrenaline and a single meal, and purine nucleotide (GDP) binding to brown adipose tissue (BAT) mitochondria were also increased. Cafeteria feeding induced hyperphagia, increases in metabolic rate, acute thermogenic responses and BAT activity, and depressed energetic efficiency. ACTH had no additional effects on energy balance, thermogenic responses or brown fat in cafeteria-fed rats. These data indicate that stimulation of thermogenesis and BAT activity by ACTH resembles that induced by hyperphagia, and this effect may be partly responsible for the changes in energy balance after adrenalectomy seen in previous studies. However, acute and chronic responses to ACTH depend upon the nutritional status of the animal.