Levels of plasma proteins in human and rat fetal CSF and the development of the blood-CSF barrier.

High levels of albumin, alpha-fetoprotein (AFP), IgG, prealbumin and transferrin have been detected in cerebro-spinal fluid (CSF) of human fetuses between 14 and 25 weeks old. The concentration of each plasma protein in CSF was found to vary during the gestational period in relation to its serum levels and rate of synthesis and as a consequence of a reduced permeability of the blood-CSF barrier after 22 weeks. In fact, the higher CSF levels of AFP were detected in fetuses about 16 weeks old, while the highest values of albumin were observed in CSF from fetuses between 20 and 24 weeks old. Experimental work has shown that also in rats the permeability of the blood-CSF barrier is incomplete during fetal and perinatal life. When 125I-labelled albumin and IgG or 14C-oestrogen and testosterone were injected intraperitoneally in newborn rats, the labelled proteins and hormones were detected in fetal blood and CSF four hours after the injection. These results are discussed in view of the suggestion that maternal abnormal states with regard to hormones and antibrain antibodies may affect the development of the nervous system and unfolding of behaviour.