The thermogenic role of adipose tissue in the dog.

Brown adipose tissue was clearly present in neonatal dogs. In the adult the tissue was superseded by a tissue with the gross characteristics of white adipose. However despite their appearance adult adipose tissue depots may contribute to non-shivering thermogenesis. Regional blood flow measurements using injected radioactive microspheres indicated large increases in blood flow to adipose depots during infusion of noradrenaline. Coupled with blood flow estimations, measurement of arteriovenous differences in dissolved oxygen across the bladder fat depot demonstrated a quantitative increase in oxygen extraction by the depot during noradrenaline infusion. Acute activation of non-shivering thermogenesis in the dog was not associated with increased mitochondrial GDP-binding in adipose tissue. However chronic treatment with a beta-stimulant (LY79730) which increased capacity for non-shivering thermogenesis was associated with increased mitochondrial GDP-binding and cytochrome oxidase activity in peri-renal adipose tissue.