Effect of norepinephrine on the Krebs cycle intermediates of brown adipose tissue in mesorectums auratus hamster

Abstract EN

This study was carried out to determine the rate-limiting and/or norepinephrine-stimulated step in the tricarboxylic acid cycle of hamster (Mesocricetus Auratus) brown adipocytes.

For this determination, citrate, malatc and a -ketoglutarate in interscapular brown fat (IBAT) were measured spectrofluorometrically before and after stimulation with norepinephrine.

Norepinephrine infusion increased both IBAT and colonic teffipevatllfc which are respectively 1.6 ± 0.2°C, 0.4 + 0.1°C.

The concentration and the total amount of citrate and malale were significantly greater in norepinephrine-stimulated than in non stimulated IBAT.

In contrast, the concentration and the total amount of cx-ketogiutarate were significantly less in stimulated as compared to nonstimulated IBAT.

The direction and magnitude of these changes support the view that a-ketogiutarate dehydrogenase is the rate-limiting step in TCA cycle of unstimulated brown adipose tissue; this enzyme is activated when brown fat is stimulated by norepinephrine, and that isocitrate dehydrogenase is most likely the rate-limiting step in the norepinephrine-stimulated brown fat.