AMINO-ACID-TRANSPORT ACROSS THE PLACENTA MEASURED BY POSITRON EMISSION TOMOGRAPHY AND ANALYZED BY COMPARTMENT MODELING

The materno-fetal transfer of methionine in the Rhesus monkey was investigated using positron emission tomography, a non-invasive in vivo tracer technique based on short-lived radionuclides. A bolus dose of [11CH3]-/-methionine was administered intravenously and the radioactivity concentrations in the placenta, the fetus and the materaal arterial blood were measured as functions of time and fitted to an equation derived from a four compartment model of the fetoplacental complex. Rate constants were calculated describing materaal placental blood flow, the transfer of [11CH3]-/-methionine to the placental tissue and the fetus. The transfer rate of methionine to the fetus was estimated as 0.8 ü 1.5 nmol/min/g placenta and was similar to the transfer to the placental tissue. An approximate blood flow through the intervillous space of 128 rnl/min was found. The correlation between placental transfer to the fetus and the maternal blood flow in the intervillous space was low. © 1990, Walter de Gruyter. All rights reserved.