Actions of sex steroids and corticosteroids on rabbit choroid plexus as shown by changes in transport capacity and rate of cerebrospinal fluid formation.

The effect of betamethasone on choroid plexus transport and CSF formation in rabbits was studied. Following 5 days of daily treatment with betamethasone the CSF production rate was reduced by 43% as measured by ventriculo-cisternal perfusion with radioactive inulin. Accordingly, the Na(+)-K(+)-ATPase activity and the transport capacity in the choroid plexus, measured in terms of choline (10(-5) M) uptake and accumulation in vitro, decreased (in the lateral ventricles by 31% in both cases). Isolated choroid plexuses from rabbits were also used to determine uptake and accumulation of choline and the activities of various types of ATPases following pretreatment of the animals with 17-beta-oestradiol, alone or in combination with progesterone. The combined treatment reduced the choline uptake by 35% and also lowered the activity of Na(+)-K(+)-ATPase by 31% without influencing tissue wet weight. Thus, the demonstrated influences of glucocorticoids and sex steroids on the transport capacity in the choroid plexus seem to be important components in their postulated effects on intracranial hypertension.