Activity of enzymes involved in norepinephrine biosynthesis in the brown adipose tissue of the developing rat.

The activities of tyrosine hydroxylase (TH) and dopamine-beta-hydroxylase (DBH) were measured in vitro in the brown adipose tissue (BAT) of control and hypothyroid developing rats. Neonatal hypothyroidism slows the development of TH activity, as manifest in lower BAT TH activity, relative to controls, up to 20 days. This effect is more pronounced when the onset of hypothyroidism is induced prenatally. No clear effect of hypothyroidism on DBH activity was evident.