Human placental norepinephrine transporter mRNA: expression and correlation with fetal condition at birth.

The purpose of this study was to determine the primary form of human placental norepinephrine transporter (hNET) mRNA expressed in the human placenta and to compare the level of expression in normal pregnancies and in pregnancies complicated by drug exposure or other forms of physiological derangement. We used the hNET cDNA to measure RNA extracted from placenta and examined placental RNA following complicated and uncomplicated pregnancies. To compare transporter expression and its relation to fetal condition at birth, umbilical arterial plasma catecholamine levels, umbilical arterial blood gases and placental transporter mRNA level were compared by linear regression analysis.

The contribution of transporter-dependent uptake to fetal catecholamine clearance.

These studies were designed to determine the contribution of cocaine-sensitive, transporter-dependent, reuptake mechanisms to the intrauterine norepinephrine clearance rate in chronically catheterized fetal sheep. Baseline norepinephrine clearance and appearance rates were 125 +/- 20 ml/kg/min and 85 +/- 11 ng/kg/min, respectively. Transporter-dependent clearance represented 40% of the intrauterine clearance rate.

Placental norepinephrine clearance: in vivo measurement and physiological role.

The intrauterine clearance rate of catecholamines is higher than in newborn animals or in adults. The separate contributions of the fetus and placenta to this clearance are not known. The placenta is a site of expression of the amine plasma membrane transporters that mediate this process.