AJP - Endocrinology and Metabolism, Vol 249, Issue 4 333-E336, Copyright © 1985 by American Physiological Society
Thermogenesis and BAT activity in hypophysectomized rats with and without corticotropin replacement
N. J. Rothwell and M. J. Stock
Surgical hypophysectomy (Hypox) suppressed body weight, body energy gain,
and net energetic efficiency when compared with pair-fed, sham-operated
controls but caused marked increases in the thermic response to food, brown
adipose tissue (BAT) mass, protein content, and BAT thermogenic activity
(estimated from mitochondrial purine nucleotide binding). Chronic
replacement of Hypox rats with ACTH restored adrenal weight, plasma
corticosterone levels, body energy gain, energetic efficiency, and the
thermic response to food to normal. However, the Hypox-replaced animals
were apparently fatter (greater carcass energy density) and retained a
greater mass of brown fat than controls. Purine nucleotide binding to BAT
mitochondria was lower in the ACTH-replaced group than in Hypox rats but
remained above the level in controls. These data indicate that
hypophysectomy stimulates thermogenesis, probably as a result of decreased
adrenal steroid release. However, ACTH does not totally prevent the effects
of Hypox, and an involvement of other pituitary hormones and/or
hypothalamic-releasing factors cannot be excluded.
