Brown adipose tissue-a factor in the survival of harp seal pups.

The respiratory characteristics of mitochondria isolated from the subcutaneous brown adipose tissue of newborn harp seals indicate that the tissue is thermogenically active. Temperature recordings in vivo revealed, in fact, that the tissue was maintained at a temperature close to that of the body core during immersion of the pups in ice-water. Beta-adrenergic blockade markedly increased the cooling rates at both locations in ice-water, while curarization, accompanied by artificial respiration did not. We conclude that nonshivering thermogenesis through activated brown adipose tissue plays a decisive role in the defence against cold in the newborn harp seal.