Studies on the Transfer of Steroid Hormones Across the Blood-Cerebrospinal Fluid Barrier in the Rhesus Monkey

Abstract

Indwelling canulae were placed in the lateral ventricles of the brains of 6 adult male rhesus monkeys [Macaca mulatta], and the movement of estradiol-17.beta. (E2), testosterone (T) and 5.alpha.-dihydrotestosterone (DHT) across the blood-cerebrospinal fluid (CSF) barrier was measured. Serial samples of blood and CSF were collected every 30 min during a 6 h infusion of the tritiated steroids, and the quantity of free steroid in the blood and CSF was determined by recrystallization to constant specific activity. During the course of the 6 h infusion, the average CSF concentration of steroid, expressed as dpm/ml, was about 3.5% of the concurrent plasma level of E2, 1.6% of the concurrent plasma level of T, and 0.08% of the concurrent plasma level of DHT. These differences in steroid transfer may be attributed to differential binding of these steroids to testosterone-estrogen-binding globulin (TeBG) in plasma.