CBG does not restrict blood-brain barrier corticosterone transport in rabbits
The metabolic clearance rate of corticosterone in rabbits is unrelated to the physiological concentration of corticosteroid binding globulin (CBG) in rabbit plasma. This suggests that corticosterone is available for transport into peripheral tissues in rabbits from the circulating CBG-bound pool, similar to what is known to occur in rat liver. This hypothesis was tested in the present studies, which investigate the transport of corticosterone into rabbit brain from the circulating rabbit or human CBG-bound pool. Corticosterone was readily exchangeable in brain capillaries in vivo from the circulating albumin-bound and rabbit or human CBG-bound pools. The involvement of specific CBG receptors on brain capillary endothelia in this process was investigated with (TH)-labeled human CBG prepared by reductive methylation. The transport of (TH)CBG across rabbit brain capillaries in vivo was immeasurably low, and no specific binding of this radiolabeled plasma protein to isolated brain capillaries in vivo was immeasurably low, and no specific binding of this radiolabeled plasma protein to isolated brain capilaries in vitro was observed at 37C during incubations up to 120 min. These studies indicate that the rabbit is a novel system for assessing the role of CBG in delivering corticosterone to peripheral tissues in vivo and that specific endothelial CBG receptors may not participate in the transport process.
- Research Organization:
- UCLA School of Medicine, Los Angeles
- OSTI ID:
- 6281002
- Journal Information:
- Am. J. Physiol.; (United States), Journal Name: Am. J. Physiol.; (United States) Vol. 251:2; ISSN AJPHA
- Country of Publication:
- United States
- Language:
- English
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59 BASIC BIOLOGICAL SCIENCES
ADRENAL HORMONES
BLOOD CIRCULATION
BLOOD VESSELS
BLOOD-BRAIN BARRIER
BLOOD-PLASMA CLEARANCE
BODY
BRAIN
CAPILLARIES
CARDIOVASCULAR SYSTEM
CENTRAL NERVOUS SYSTEM
CLEARANCE
CORTICOSTEROIDS
CORTICOSTERONE
GLOBULINS
GLUCOCORTICOIDS
HORMONES
HYDROXY COMPOUNDS
KETONES
LABELLED COMPOUNDS
MEMBRANE TRANSPORT
NERVOUS SYSTEM
ORGANIC COMPOUNDS
ORGANS
PREGNANES
PROTEINS
RECEPTORS
STEROID HORMONES
STEROIDS
TRITIUM COMPOUNDS