Effect of acute cold exposure on norepinephrine turnover rates in rat white adipose tissue

The present studies were carried out to assess directly sympathetic activity in white adipose tissue in response to cold exposure. Norepinephrine (NE) content and NE turnover rates were determined in epididymal and retroperitoneal adipose tissue from rats exposed to cold (4 degrees C) and controls kept at ambient temperature. Parallel measurements were made in interscapular brown adipose tissue (IBAT), in which activation of catecholaminergic innervation by cold exposure is well known. Exposure to 4 degrees C for 4 h reduced the endogenous NE content by 50% in IBAT and by 30% in both epididymal and retroperitoneal adipose tissues. Compared to warm controls, average values of fractional rates of turnover and cf turnover rates, estimated with alpha-methyl-tyrosine, increased 5-fold in IBAT and 2.5-3-fold in epididymal and retroperitoneal tissues from rats exposed to cold. The present data provide the first direct evidence that white adipose tissue sympathetic activity is increased during acute cold exposure.