To allow recovery and assure integrity of the isolated perfused
cotyledon, experiment are preceded by a period of open perfusion
(pre-phase) of both compartments [28]. Thereafter, experiments can
be performed by using either closed (recirculating) or the open (nonrecirculating)
method. Recirculating studies imitate physiological
conditions and can be used to study transplacental transfer and
metabolism, in open perfusions drug clearance can be studied.