Aging and the blood-brain barrier: Changes in the carrier-mediated transport of peptides in rats
1985; Elsevier BV; Volume: 61; Issue: 1-2 Linguagem: Inglês
10.1016/0304-3940(85)90420-3
ISSN1872-7972
AutoresWilliam A. Banks, Abba J. Kastin,
Tópico(s)Macrophage Migration Inhibitory Factor
ResumoAge-related changes in the brain's saturable, specific, carrier-mediated transport system for the small, N-tyrosinated peptides Tyr-MIF-1 (Tyr-Pro-Leu-Gly-NH2) and methionine-enkephalin (Met-Enk) were studied in Fischer 344 rats aged 4 and 26 months. These studies showed statistically significant differences between the two age groups for both the Tmax (transport maximum) [3.22 ± 0.013 nmol/min/g (young rats, mean ± S.E.M.) vs 2.41 ± 0.009 nmol/min/g (aged rats)] and T50 (the amount required to achieve 50% of that maximum) [84.9 ± 1.0 nmol/g (young) vs 65.1 ± 0.60 nmol/g (aged)]. The T50:Tmax ratio was nearly equal for the two groups: 26.4 (young) vs 26.9 (aged), consistent with the uncompetitive type of inhibition indicative of alterations in the substrate-carrier complex. In addition, blood concentrations of Tyr-MIF-1-like immunoactivity were nearly doubled in aged rats (3.24 ± 0.373 vs 1.67 ± 0.0904 pM/ml), while blood concentrations of Met-Enk-like immunoactivity and brain concentrations of immunoactive Tyr-MIF-1 and Met-Enk showed no statistically significant difference between age groups. Thus, a carrier-mediated system responsible for the transport of peptides across the blood-brain barrier undergoes changes with aging.
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