On the blood-brain barrier to peptides: [3H]beta-casomorphin-5 uptake by eighteen brain regions in vivo.
After intracarotid injection of [3H]beta-casomorphin-5 (beta CM5) in rats, the accumulation of radioactivity was determined in 18 brain regions and the anterior pituitary. The relative accumulation in all regions significantly exceeded that of [3H]inulin by a factor of 2.5, indicating a low but measurable brain uptake of the peptide. In blood-brain barrier-free areas, the accumulation of radioactivity was 15-fold higher than in blood-brain barrier-protected areas. The relative accumulation was not dependent on the total beta CM5 concentration in the range of 0.3-1.1 microM, and was not depressed by 400 microM L-tyrosine. We conclude that beta CM5, like other peptides, is accumulated in the blood-brain barrier-free areas to a relatively high but differing degree, whereas in the areas with a tight endothelium the accumulation is relatively low and nearly uniform. A binding to endothelial cells may contribute to the low accumulation of beta CM5, especially in blood-brain barrier-protected areas.
D000818:Animals; D001812:Blood-Brain Barrier; D001921:Brain / Q000378:metabolism*; D002339:Carotid Arteries; D004723:Endorphins / Q000008:administration & dosage / Q000378:metabolism*; D007269:Injections, Intra-Arterial; D008297:Male; D010446:Peptide Fragments; D010903:Pituitary Gland, Anterior / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D014018:Tissue Distribution
D004723:Endorphins; D010446:Peptide Fragments; C034812:beta-casomorphin 5