Techniques to study human placental transport

Pregnancy in the 20th century involves women of many age groups from early teens to the fourth or fifth decade. Modern medicine and in vitro fertiliza tion techniques have increased options for pregnancy and childbirth. Pregna ncy is a dynamic state, and medical concerns may involve disorders of the f etus and mother requiring medications and special nutrients. Therefore, dif ferent techniques have been developed to evaluate the placental transfer of drugs and nutrients using tissues and cells derived from human placenta. T hese include (a) isolated tissues and cells to study placental transport, ( b) primary and malignant trophoblast cell cultures and (c) biophysical meth ods for studying placental transport. Also, convenient study models have be en developed to evaluate placental transfer of safe drugs in pregnant women . Some of the drugs studied by these techniques and models include (a) anes thetics and pain medications used during delivery, (b) antibiotics and anti -bacterials used to cure infections, (c) drugs abused by pregnant women and (d) nutrients required for proper fetal growth. Placental transfer and exc hange mechanisms are complicated processes, and in vitro models reflect onl y partially the equilibria that exist among mother, placenta and fetus. The perfused cotyledon model is elegant and simple but gives only restricted i nformation. Isolated placental tissues give useful information about the ph armacological effects of drugs. Metabolic studies using human placental mod els provide information on the metabolism of a drug during placental transf er and accumulation of the drug or its metabolite in the placenta or fetal circulation. Several studies on the transplacental passage of drugs exist b ut many questions regarding the transfer of drugs between the maternal and fetal circulations and clearance of drugs from fetal circulation have yet t o be answered. This article reviews in vitro and in vivo methods for evalua tion of transplacental transport of drugs and their current effectiveness t o obtain clinically useful data. (C) 1999 Elsevier Science B.V. All rights reserved.