Regression of brown adipose tissue mitochondrial function and structure in neonatal goats.

Rapidly regressing perirenal brown adipose tissue (BAT) of neonatal goats was studied to correlate changes in mitochondrial metabolism and thermogenic capacity with changes in mitochondrial structure. The alpha-glycerophosphate shuttle activity of perirenal BAT mitochondria declined 60% from birth to 6 days of age. Oxygen consumption and thermogenic capacity measured by ion conductance peaked at birth and declined to low levels at 6 days. Sample electron micrographs of perirenal BAT showed intact electron-dense mitochondria with many cristae and little matrix area at 2 days. However, by 6 days the mitochondria were very relaxed with large matrix area, few cristae, and observable degradation. These results indicate that the morphological changes exhibited by rapidly regressing goat's perirenal BAT in the 1st wk postpartum are accompanied by dramatic alterations in BAT mitochondrial function.