Blood-brain transport of thiamine monophosphate in the rat: a kinetic study in vivo.
To calculate the kinetic parameters of thiamine monophosphate transport across the rat blood-brain barrier in vivo, different doses of a [35S]thiamine monophosphate preparation with a specific activity of 14.8 mCi.mmol-1 were injected in the femoral vein and the radioactivity was measured in arterial femoral blood and in the cerebellum, cerebral cortex, pons, and medulla 20 s after the injection. This short experimental time was used to prevent thiamine monophosphate hydrolysis. Thiamine monophosphate was transported into the nervous tissue by a saturable mechanism. The maximal transport rate (Jmax) and the half-saturation concentration (Km) equaled 27-39 pmol.g-1.min-1 and 2.6-4.8 microM, respectively. When compared with that of thiamine, thiamine monophosphate transport seemed to be characterized by a lower affinity and a lower maximal influx rate. At physiological plasma concentrations, thiamine monophosphate transport rate ranged from 2.06 to 4.90 pmol.g-1.min-1, thus representing a significant component of thiamine supply to nervous tissue.
Patrini
C
C
Institute of Human Physiology, University of Pavia, Italy.
Reggiani
C
C
Laforenza
U
U
Rindi
G
G
D000818:Animals; D001692:Biological Transport; D001812:Blood-Brain Barrier; D001921:Brain / Q000378:metabolism*; D002531:Cerebellum / Q000378:metabolism; D002540:Cerebral Cortex / Q000378:metabolism; D007700:Kinetics; D008297:Male; D008526:Medulla Oblongata / Q000378:metabolism; D011149:Pons / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D013831:Thiamine / Q000031:analogs & derivatives*; D013833:Thiamine Monophosphate / Q000097:blood / Q000378:metabolism*
D013833:Thiamine Monophosphate; D013831:Thiamine