Functional development of adrenergic uptake mechanisms in the human fetal heart.

The uptake of 3H-NA into human fetal heart tissue was low during the first half of gestation, only one-fifth of that observed in the mouse heart. A gradual increase in uptake was seen during the second trimester of gestation. A drop in temperature resulted in inhibition of 3H-NA uptake in all samples, but most distinctly in the mouse heart and in the human fetal heart at 14-20 weeks of gestation. Cocaine and desipramine reduced the uptake of 3H-NA in human fetal atria after 14 weeks of gestation but not before that. Nialamide showed no such effect. The functional development of the noradrenergic nervous system in the human fetal heart was found to be very slight during the first trimester of pregnancy. After that a gradual maturation of noradrenergic mechanisms was seen. At the end of the first half of gestation the noradrenergic neurons in the human fetal heart may be held to function qualitatively similarly to those in the mature mouse heart.