Species-dependent variables in blood cerebrospinal fluid barrier for proteins.

Cerebrospinal fluid/plasma concentration quotients for immunoglobulin G (I) and albumin (A) were determined in guinea pigs. Age and sex-dependent influences on these quotients (I/A) were analyzed and compared with the values for human lumbar, cisternal and ventricular cerebrospinal fluid. The ratio I/A, which characterizes the molecular size-dependent selectivity of the blood cerebrospinal fluid barrier function for proteins, was found to be a constant in a single species, but showed marked interspecies differences.