Different responses of white and brown adipose tissue to drugs affecting lipolysis

5 Carboxyl-3 methylpyrazole (5C3MP) and nicotinic acid are very effective in lowering FFA in plasma and white adipose tissue but not in brown adipose tissue under conditions of FFA mobilization obtained by fasting and cold and by the administration of norepinephrine, theophylline and ACTH. Similar results were obtained also in vitro except that in this case the effect of theophylline on brown adipose tissue was also slightly inhibited by 5C3MP. PGE ₁ inhibited the effect of norepinephrine and theophylline on white but not on brown adipose tissue. The results obtained indicate that in vivo the level of FFA in plasma depends more on the lipolysis occurring in the white than in the brown adipose tissue.