Suppression of cerebrospinal fluid (CSF) production by a Na+/K+ pump inhibitor extracted from human cerebrospinal fluid.

A low molecular weight compound (about 600 daltons) extracted from human cerebrospinal fluid, and sensitive to proteolytic enzymes, has been shown to mimic the specific inhibitory effects of cardiac glycosides on the Na+/K+ pump of erythrocytes. The compound, which was labelled CSF-inhibitor (CSF-I) and reconstituted in artificial rabbit CSF, was used to study its effects on the rate of CSF formation in rabbits. Three groups of adult New Zealand white rabbits of either sex, anesthetized with ketamine and xylazine, and artificially respired were subjected to ventriculocisternal perfusions. Baseline rates of CSF formation were obtained during the first 2 hours of perfusion when plain rabbit CSF was used as the perfusate. Thereafter, the animals were perfused for an additional 2 to 3 hours with either plain rabbits CSF (controls), rabbit CSF containing 10(-6) M ouabain (group 2) or CSF-I (group 3). The rate of CSF formation in control animals was observed to gradually decline with time (about 7.5% in 4 hours). The addition of ouabain to the perfusate caused an abrupt and marked 43% decline in the rate of formation while the addition of CSF-I resulted in a 57% decline. These results suggest that the peptide CSF-I which is present in human CSF may act as an endogenous regulator of CSF production.