In situ lipolysis measured by in vivo microdialysis during acute cold exposure

The lipolytic responsiveness of interscapular white adipose tissue was measured, in male Sprague-Dawley rats (355 +/- 12 g, n = 7), by microdialysis before, during, and after an acute cold exposure (1 h at 4 degrees C). Microdialysis probes were perfused with standard Krebs-Ringer buffer to determine basal and stimulated rates of lipolysis. The concentration of glycerol in the dialysate was measured and considered as the lipolytic index. During the experiment, energy expenditure was measured by indirect calorimetry. Cold exposure at 4 degrees C doubled energy expenditure. At the same time, it resulted in a 2.7-fold increase in glycerol release. The present study shows that microdialysis is a perfectly adapted tool to investigate in vivo regulation of adipose tissue on awake, unrestrained rats.