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.
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Titolo: | Blood-brain transport of thiamine monophosphate in the rat: a kinetic study in vivo. | |
Autori: | ||
Data di pubblicazione: | 1988 | |
Rivista: | ||
Abstract: | 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. | |
Handle: | http://hdl.handle.net/11571/108734 | |
Appare nelle tipologie: | 1.1 Articolo in rivista |