Effects of Single Cortisone Injections on Brown Adipose Tissue of Developing Rats

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Abstract
An injection of a single dose of cortisone acetate (5 mg/100 g body weight) to 9-day-old rats resulted in the following changes in brown adipose tissue 24 h later: (1) the fresh weight was increased due to fat accumulation; (2) the DNA content of whole interscapular brown fat stayed unaltered, while the RNA content was increased; (3) specific activities of cytoplasmic alpha-glycerophosphate dehydrogenase and malic enzyme were increased; (4) the percentage of mitochondrial protein in the whole tissue protein was not changed, but mitochondria seemed to be more fragile, fewer were recovered by a standard isolation procedure, and more cytochrome c oxidase contaminated the microsomal fraction; (5) mitochondrial alpha-glycero-phosphate dehydrogenase and succinate dehydrogenase activities were decreased per milligram homogenate protein and (in isolated mitochondrial fraction) per milligram mitochondrial protein; (6) the endogenous respiration of brown fat mitochondria was activated much less by carnitine and CoA; and (7) CO2 formation from palmitate-14C by isolated mitochondria was considerably lower.A similar injection to 30-day-old rats had no significant effect.It is suggested that a single injection of cortisone affects the mitochondrial structure of brown adipose tissue and the ability to oxidize fatty acids and that it is effective on day 10 but not on day 30.

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