The effect of nicotinic acid on adipose tissue metabolism in vitro.

Rat epididymal fat pads were incubated in vitro in the presence of norepinephrine and nicotinic acid. Nicotinic acid was found to inhibit the glycerol release induced by norepinephrine from the tissues. It also increased glucose uptake. The lipase activity in the tissue homogenate was increased by norepinephrine. This increase was more pronounced in the presence of norepinephrine and glucose. Nicotinic acid incubated with the intact tissue inhibited the norepinephrine-induced increase. It had no effect when added to the homogenate. The results suggest that the ability of nicotinic acid to decrease fatty acid outflow from adipose tissue is caused by inhibition of the lipase activation by norepinephrine and possible also by increase of re-esterification of fatty acids.