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

Abstract

Indwelling canulae were placed in the lateral ventricles of the brains of six adult male rhesus monkeys, and the movement of estradiol-17beta (E2), testosterone (T), and 5alpha-dihydrotestosterone (DHT) across the blood-cerebrospinal fluid (CSF) barrier was measured. Serial samples of blood and CSF were collected every 30 minutes during a 6 hour 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-hour 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. It is proposed that these differences in steroid transfer can be attributed to differential binding of these steroids to testosterone-estrogen-binding globulin (TeBG) in plasma.