Relationship between arterial and cisternal CSF oxygen tension in rabbits.

Oxygen tension was measured in samples of blood and cisternal cerebrospinal fluid taken from anesthetized, paralyzed, and mechanically ventilated rabbits at various levels of arterial PO2. Cerebrospinal fluid oxygen tension (CSF PO2) was correlated with arterial PO2 (linear regression equation PCSFO2 = 0.2472 Pao2 + 42.34). During hypoxia CSF PO2 was higher than arterial PO2 in most experiments. These data can be attributed to the Bohr effect, which would increase the PO2 of the blood in choroid plexus capillaries as a result of its acidification. The acidification was suggested by Maren (Am. J. Physiol. 222: 885-889, 1972) to be a part of the ionic exchanges involved in cerebrospinal fluid formation. Such a mechanism may be of importance for supporting choroid plexus metabolism and function during hypoxia. This mechanism is most clearly seen in the rabbit.