Figure 4a-c. Percentage Distribution following systemic administration of glucocorticoids in abcb1a/b (+/+) and abcb1a/b (-/-) mice.

[³H]dexamethasone (8.9μCi/ml; 3.9 pM, Fig. 4a), [³H]cortisol (1.6 ng/g; 58.0μM, Fig. 4b), or [³H]corticosterone (1.7 ng/g; 58.9μM, Fig. 4c) was prepared in 0.9% saline solution. Mice (6 or 7/strain) were subcutaneously injected with radiolabeled drugs, allowed to rest for 2 hours, then decapitated; the pituitary gland, cerebellum, and remaining brain matter were separated and individually weighed. Samples were then prepared for liquid scintillation counting. The concentration of radioactivity in the brain tissue (dpm g-1) is expressed as a percentage of that in the injectate (dpm ml-1). The uptake of [³H]dexamethasone into the cerebellum and remaining brain was significantly increased in abcb1a/b (-/-) mice (open, white bar) compared to abcb1a/b (+/+) mice (solid, black bar), and the uptake of [³H]dexamethasone was not significantly increased in the pituitary gland of abcb1a/b (-/-) mice compared to abc1a/b (+/+) mice. The uptake of [³H]cortisol was significantly increased in the cerebellum and remainder brain of abcb1a/b (-/-) mice (open, white bar) compared abcb1a/b (+/+) mice (solid, black bar), and uptake of [³H]cortisol was not significantly increased in the pituitary gland between abcb1a/b (-/-) mice compared to abcb1a/b (+/+) mice. The uptake of [³H]corticosterone into the remainder brain was significantly increased in abcb1a/b mice (open, white bar) compared to abcb1a/b (+/+) mice (solid, black bar). There was no significant difference between strains in the uptake of [³H]corticosterone in the cerebellum or pituitary gland. * denotes significance of P<0.05, Student’s t-test.