Uptake of 3-O-methyl-D-[U-14C]glucose into brain of rainbow trout: possible effects of melatonin.
The influx of glucose into the brain and plasma glucose disappearance were estimated in rainbow trout (Oncorhynchus mykiss) intravenously injected (1 ml x kg(-1) body weight) with a single dose (15 microCi x kg(-1) body weight) of 3-O-methyl-D-[U-14C]glucose ([U-14C]-3-OMG) at different times (2-160 min), and after intravenous injection at 15 min of increased doses (10-60 microCi x kg(-1) body weight) of [U-14C]-3-OMG. Brain and plasma radiotracer concentrations were measured, and several kinetic parameters were calculated. The apparent brain glucose influx showed a maximum after 15-20 min of injection then decreased to a plateau after 80 min. Brain distribution space of 3-OMG increased from 2 min to 20 min reaching equilibrium from that time onwards at a value of 0.14 ml x g(-1). The unidirectional clearance of glucose from blood to brain (k1) and the fractional clearance of glucose from brain to blood (k2) were estimated to be 0.093 m x min(-1) x g(-1), and 0.867 min(-1), respectively. A linear increase was observed in brain and plasma radiotracer concentrations when increased doses of [U-(14)C]3-OMG were used. All these findings support a facilitative transport of glucose through the blood-brain barrier of rainbow trout with characteristics similar to those observed in mammals. The injection of different doses of melatonin (0.25-1.0 mg x kg(-1)) significantly increased brain glucose influx suggesting a possible role for melatonin in the regulation of glucose transport into the brain.
Aldegunde
M
M
Departamento de Fisioloxía, Facultade de Bioloxía, Universidade de Santiago de Compostela, Spain. fsaldegu@usc.es
Andrés
M D
MD
Soengas
J L
JL
D019325:3-O-Methylglucose / Q000493:pharmacokinetics*; D000818:Animals; D001812:Blood-Brain Barrier / Q000187:drug effects* / Q000502:physiology; D001923:Brain Chemistry / Q000502:physiology*; D002250:Carbon Radioisotopes / Q000493:pharmacokinetics; D008550:Melatonin / Q000494:pharmacology*; D017686:Oncorhynchus mykiss / Q000378:metabolism*
D002250:Carbon Radioisotopes; D019325:3-O-Methylglucose; D008550:Melatonin