In vitro alanine utilization by rat interscapular brown adipose tissue

The in vitro oxidation to CO2 and tissue incorporation of alanine label by pieces of rat interscapular brown adipose tissue (IBAT) has been investigated. Insulin increased both uptake and oxidation of alanine, as well as the incorporation of alanine label into tissue. This effect only was observed in the presence of glucose in the incubation medium. Noradrenaline hampered alanine incorporation, not affecting its rate of oxidation. IBAT from 4-h cold-exposed rats showed a higher alanine utilization than that of controls; however, IBAT pieces from both 36-h starved and 30-day cold-exposed rats presented lower rates of alanine utilization. The main fate of alanine taken up by the IBAT pieces was its oxidation to CO2. Part of the label was also incorporated into the fatty acid fraction of lipids. The results obtained in this study agree with a possible role of alanine as alternative energetic substrate for IBAT.