Post-natal development of interscapular (brown) adipose tissue in the guinea pig: effect of environmental temperature.

The post-natal development of interscapular brown adipose tissue (BAT) was studied in the guinea pig by monitoring changes in DNA, triglycerides and mitochondrial protein as well as the activity of cytochrome oxidase and atractyloside insensitive GDP-binding. The results demonstrate that neonatal brown fat develops into a tissue with the gross characteristics of white adipose tissue. In this respect the post-natal development of guinea pig BAT is analogous to that of the tissue in man. Furthermore the apparent transformation is not irreversible since cold exposure (+4 degrees C) of adult guinea pigs for six weeks resulted in restoration of cytochrome oxidase, GDP-binding, etc, to levels characteristic of neonatal BAT. However, the interscapular fat pad temperature response to noradrenaline and the presence of 32 000 mol. wt mitochondrial inner membrane protein indicate that the tissue retains thermogenic activity even in warm acclimated adult guinea pigs.