Effects of Barbiturates on Facilitative Glucose Transporters are Pharmacologically Specific and Isoform Selective (original) (raw)
1999, The Journal of Membrane Biology
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Interactions of sodium pentobarbital with d-glucose and l-sorbose transport in human red cells
Biochimica Et Biophysica Acta - Biomembranes, 1999
Pentobarbital acts as a mixed inhibitor of net D-glucose exit, as monitored photometrically from human red cells. At 30³C the K i of pentobarbital for inhibition of V max of zero-trans net glucose exit is 2.16 þ 0.14 mM; the affinity of the external site of the transporter for D-glucose is also reduced to 50% of control by 1.66 þ 0.06 mM pentobarbital. Pentobarbital reduces the temperature coefficient of D-glucose binding to the external site. Pentobarbital (4 mM) reduces the enthalpy of D-glucose interaction from 49.3 þ 9.6 to 16.24 þ 5.50 kJ/mol (P 6 0.05). Pentobarbital (8 mM) increases the activation energy of glucose exit from control 54.7 þ 2.5 kJ/mol to 114 þ 13 kJ/mol (P 6 0.01). Pentobarbital reduces the rate of L-sorbose exit from human red cells, in the temperature range 45³C^30³C (P 6 0.001). On cooling from 45³C to 30³C, in the presence of pentobarbital (4 mM), the K i sorboseY glucose decreases from 30.6 þ 7.8 mM to 14 þ 1.9 mM; whereas in control cells, K i sorboseY glucose increases from 6.8 þ 1.3 mM at 45³C to 23.4 þ 4.5 mM at 30³C (P 6 0.002). Thus, the glucose inhibition of sorbose exit is changed from an endothermic process (enthalpy change = +60.6 þ 14.7 kJ/mol) to an exothermic process (enthalpy change = 343 þ 6.2 7 kJ/mol) by pentobarbital (4 mM) (P 6 0.005). These findings indicate that pentobarbital acts by preventing glucose-induced conformational changes in glucose transporters by binding to`non-catalytic' sites in the transporter.
Interactions of sodium pentobarbital with ?-glucose and ?-sorbose transport in human red cells
Biochimica et Biophysica Acta (BBA) - Biomembranes, 1999
Pentobarbital acts as a mixed inhibitor of net D-glucose exit, as monitored photometrically from human red cells. At 30³C the K i of pentobarbital for inhibition of V max of zero-trans net glucose exit is 2.16 þ 0.14 mM; the affinity of the external site of the transporter for D-glucose is also reduced to 50% of control by 1.66 þ 0.06 mM pentobarbital. Pentobarbital reduces the temperature coefficient of D-glucose binding to the external site. Pentobarbital (4 mM) reduces the enthalpy of D-glucose interaction from 49.3 þ 9.6 to 16.24 þ 5.50 kJ/mol (P 6 0.05). Pentobarbital (8 mM) increases the activation energy of glucose exit from control 54.7 þ 2.5 kJ/mol to 114 þ 13 kJ/mol (P 6 0.01). Pentobarbital reduces the rate of L-sorbose exit from human red cells, in the temperature range 45³C^30³C (P 6 0.001). On cooling from 45³C to 30³C, in the presence of pentobarbital (4 mM), the K i sorboseY glucose decreases from 30.6 þ 7.8 mM to 14 þ 1.9 mM; whereas in control cells, K i sorboseY glucose increases from 6.8 þ 1.3 mM at 45³C to 23.4 þ 4.5 mM at 30³C (P 6 0.002). Thus, the glucose inhibition of sorbose exit is changed from an endothermic process (enthalpy change = +60.6 þ 14.7 kJ/mol) to an exothermic process (enthalpy change = 343 þ 6.2 7 kJ/mol) by pentobarbital (4 mM) (P 6 0.005). These findings indicate that pentobarbital acts by preventing glucose-induced conformational changes in glucose transporters by binding to`non-catalytic' sites in the transporter.
Effect of repeated sodium pentobarbitone administration on glucose homeostasis in mice
General Pharmacology: The Vascular System, 1980
Glucose tolerance tests were conducted in conscious and pentobarbitone-anaesthetized mice after daily administration of an anaesthetic dose of sodium pentobarbitone (45 mg/kg) for 10 consecutive days. 2. Mice examined in the conscious state showed impaired glucose tolerance and reduced plasma insulin concentrations compared with conscious controls. 3. Mice examined in the anaesthetized state also showed reduced insulin concentrations, although glucose tolerance was not significantly altered in comparison with anaesthetized controls. 4. Whereas 10 days of pentobarbitone treatment reduced insulin concentrations, the induction of pentobarbitone anaesthesia heightened the insulin response to glucose in both untreated and 10 day treated mice compared with conscious controls. 5. The results demonstrate that 10 consecutive daily treatments with an anaesthetic dose of pentobarbitone impair glucose homeostasis and lower plasma insulin concentrations in mice.
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