Transport of nutrients and hormones through the blood-brain barrier
Abstract
An understanding of the mechanisms of transport of circulating nutrients and hormones through the brain capillary wall, i.e., the blood-brain barrier, is important because the availability in brain of these substances influences a number of cerebral metabolic pathways. For example, the utilization by brain of glucose, ketone bodies and branched chain amino acids or the production of monoamines, acetylcholine, carnosine, and nucleosides may under certain conditions be influenced by BBB transport of circulating precursor nutrients. Steroid and thyroid hormones readily traverse the BBB via lipid-mediation and carrier-mediation, respectively. Although the steroid and thyroid hormones are tightly bound by plasma proteins, protein-bound hormone, not the free (dialyzable) moiety, is the major plasma fraction transported through the BBB. With regard to circulating peptides, the available evidence indicates peptides rapidly distribute into brain interstitial space of the circumventricular organs of brain, i.e., about six small regions around the ventricles which lack a BBB. Conversely, the absence of peptide carriers in the BBB prevents the rapid distribution of peptides into the vast majority of brain interstitial or synaptic spaces. H...Continue Reading
References
Newborn rabbit blood-brain barrier is selectively permeable and differs substantially from the adult
Citations
Lack of effect of beta-endorphin on basal or glucagon-stimulated hepatic glucose production in vitro
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