Sympatho-adrenal activity and metabolic responses in fasted rats--the role of interscapular brown adipose tissue

Dependence of the sympatho-adrenal activity on the nutritional status in corticosterone treated rats

1. An integrated sympatho-adrenal (SA) activity, expressed in terms of urinary catecholamines (CA) excretion, and direct sympathetic activity in the interscapular brown adipose tissue (IBAT), expressed in terms of noradrenaline (NA) turnover, were studied in corticosterone treated stock fed and sucrose overfed rats. 2. Corticosterone in stock fed rats significantly decreased both the rate of IBAT NA turnover and its mass as well as urinary NA excretion but did not change either IBAT NA content, urinary adrenaline excretion or adrenal CA content. 3. Sucrose overfeeding significantly increased SA activity, i.e. the rate of NA turnover in the IBAT and urinary excretion of CA. However, corticosterone did not inhibit the sucrose-induced sympathetic nervous system activation but potentiated the activity of adrenal medulla. 4. The results suggest that the effect of corticosterone treatment on the SA activity in rats is dependent, in addition to other factors, on the nutritional status of the animals.

Implications of interscapular brown adipose tissue removal and sucrose overfeeding on the sympatho-adrenal activity and metabolic responses

1. The influence of sucrose overfeeding on the sympatho-adrenal (SA) and metabolic responses was studied in sham-operated (SHAM) rats and in those with interscapular brown adipose tissue (IBAT) removed. 2. Sucrose feeding significantly increased the SA activity, mobilized the free fatty acids (FFA), but did not change glucose homeostasis in sham-operated rats. 3. IBAT removal in control rats fed a stock diet modified the SA activity whereas the levels of both blood glucose and serum FFA were unchanged. 4. However, sucrose in rats void of IBAT potentiated the activity of sympathetic nervous system only and prevented the FFA rise, which is seen in sham-operated sucrose fed rats indicating that the enhanced level of serum FFA in these animals principally originated from the IBAT.