Proteins in cerebrospinal fluid and plasma of fetal rats during development

Abstract

The concentrations of total protein, albumin, and α -fetoprotein have been measured in the cerebrospinal fluid (csf) and plasma of fetal (12 to 22 days gestation) and neonatal (0 to 10 days postnatal) rats. Total protein concentration in cisternal csf increased from about 140 mg/100 ml at 12 days to reach a peak of over 300 mg/100 ml around the time of birth. In the postnatal period the total protein concentration declined to about 100 mg/100 ml at 10 days; the adult value was 24±8 mg/100 ml. There was substantially more α -fetoprotein than albumin in csf at 12 days gestation. Both increased in concentration toward the end of gestation; α -fetoprotein reached a plateau of about 100 mg/100 ml at 17–19 days after which it declined markedly to about 5 mg/100 ml at 10 days postnatal; albumin reached a plateau in csf of about 90 mg/100 ml around the time of birth and declined subsequently. Albumin and α -fetoprotein constituted over 50% of the total protein concentration in csf at all fetal ages studied. In plasma these two proteins made up only 35% of the total protein at 17 days gestation but by the time of birth their contribution had doubled. Total protein concentration in plasma increased throughout the developmental period studied as did that of albumin. α -Fetoprotein was at its highest concentration (440 mg/100 ml) at 19 days gestation; it declined markedly in the postnatal period. Other proteins identified in csf and plasma were: transferrin, α 1 -antitrypsin, and IgG. Evidence is discussed which suggests that the high concentration of protein in fetal csf results from specific transfer of plasma protein across the developing choroid plexus rather than from immaturity of the blood-csf barrier.