[Hydro-osmotic activity of the cerebrospinal fluid in fetuses, children and adults].

The hydroosmotic activity of the cerebrospinal fluid in 38 persons of different ages and in 2 fetuses was investigated. In the fetal cerebrospinal fluid the hydroosmotic activity was undetectable. The highest hydroosmotic activity was observed in the cerebrospinal fluid of children aged 0 to 3 years (24.320 +/- 3530 microhydroosmotic units (mHOU/ml). The activity significantly decreased in the cerebrospinal fluid of children 7 to 10 years of age (13.184 +/- 2112 mHOU/ml, p < 0.01). The above activity was detected in 40% of the adult patients with different diseases and in all the cases of idiopathic diabetes insipidus. The hydroosmotic activity of both children and adults was sensitive to trypsin digestion. The data obtained suggest the presence of a basic peptide, probably arginine-vasotocin, in the cerebrospinal fluid studied. If this hypothesis is right, vasotocin occurres in the cerebrospinal fluid only after birth and decreases with age, with the exception of some cases of pathology.