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Glucose utilization (GU) in the mouse brain in vivo was measured by the simultaneous use of [ 14 C]2-deoxyglucose (2DG), the glucose analogue that can be phosphorylated in the brain, and [ 3 H]3-O-methylglucose (3MG), the nonmetabolizable glucose analogue. Originally, this method was developed by Gjedde et al. (1985) in the rat and in humans. The present study examined the validity of this method in the mouse brain. The effects of urethane and pentobarbital (PB) on GU were also studied. Whereas the distribution volume of 3MG reached a constant value under each condition after 10 min of the tracer circulation, the apparent volume of distribution of 2DG, which increased with time in the awake mice, did not increase so greatly in the anesthetized and hypothermie mice, indicating that the net rate of 2DG phosphorylation is lowered under these conditions. These data were fitted for the conventional three-compartmental model and the values of rate constants of influx (K 1 ), efflux (k 2 ), phosphorylation, and dephosphorylation for 2DG, and K 1 and k 2 for 3MG were computed by nonlinear least square regression method. No significant difference in the value of K 1 k 2 , the distribution volume of the precursor pool, was observed between 2DG and 3MG, indicating that 3MG can be used to estimate the distribution volume of unmetabolized 2DG in the brain. The values of GU calculated from the values of estimated parameters were not significantly different from those calculated from blood and tissue radioactivities obtained during 10 min after the injection of the tracers in both awake and PB-anesthetized mice. These findings indicate that the double tracer technique is useful for measuring GU in a short duration experiment.

The effect of chlorpromazine hydrochloride (CPZ) (1-500 microM) on plasma membrane permeability and mitochondrial respiratory function of isolated rat hepatocytes was studied. The endogenous oxygen consumption stimulated by 1 mM succinate was increased significantly by 5 microM CPZ, whereas the ability to exclude trypan blue (TB) was decreased significantly by 100 microM CPZ. The release of a cytosomal enzyme, lactate dehydrogenase (LDH), was increased significantly by 50 microM CPZ, whereas the release of glutamic-opalacetic transaminase (GOT) was increased significantly by 100 microM. The endogenous oxygen consumption was decreased significantly by 150 microM CPZ. The respiration control ratio by 2 microM carbonylcyanide-m-chlorphenyl hydrazon (CCP) showed significant decreases at all concentrations of CPZ studied; and this might be attributable to the suppression by CPZ of the respiratory stimulation induced by CCP. The results indicated that CPZ at a low concentration (5 microM) first produced a significant change in plasma membrane permeability to low molecular substances such as succinate and then at higher concentrations (50-100 microM) produced significant release of the cytosomal and mitochondrial enzymes, LDH and GOT. They also indicated that the concentrations of CPZ which produced significant effects on respiratory function were higher (above 150 microM) than those which produced significant changes in plasma membrane permeability of hepatocytes.

A physiologically based pharmacokinetic model including fourteen compartments (artery, vein, and twelve tissues) was used to predict plasma and tissue ftorafur concentrations in rats after a 100 mg kg i.v. dose. Fairly good agreement was obtained between the predicted and observed time courses of ftorafur concentrations in plasma and tissues. This model was also used to predict plasma ftorafur concentrations for man. Fairly good agreement was again obtained between the predicted and observed plasma ftorafur concentrations. Additionally, it was ascertained that the ratio of body weight (kg) to distribution volume (liter) of ftorafur was approximately 1:1 in man, rat, monkey, dog and rabbit, and the ratio of body weight (kg) to total body clearance ( ml min ) was the same in all cases except rabbit.

To elucidate the characteristics of promotion factor(s) in rat serum required for the protein-mediated transport of drugs into the brain, we examined the brain uptake of DL -propranolol as a model drug using the in vivo brain uptake index ( BUI ) method in rats. The protein-mediated transport was not observed in rats injected with the buffer solution containing either various concentrations of purified rat α 1 -acid glycoprotein ( α 1 -AGP) or rat albumin. When the filtrate from rat serum was used as an injection vehicle to which a physiological concentration of purified rat serum protein(s) was added, the protein-mediated transport of DL -propranolol was observed in the rat brain. Moreover, the ability of protein-mediated transport of DL -propranolol was reduced in rats injected with the dialyzed serum compared with the undialyzed serum. These results suggest that the dialyzable promotion factor in serum is required for the protein-mediated transport of DL -propranolol into the brain.

Pharmacokinetic study of human epidermal growth factor (hEGF) in rats was performed in vivo . The hepatic extraction ratio ( E H ) of [ 125 I]hEGF, determined from the difference between the artery and the hepatic vein plasma concentrations at steady state, was 0.19. The hepatic clearance ( CL H : 7.56 ml/min/kg body wt), calculated by multiplying ( E H ) by the hepatic plasma flow rate ( Q P , H ), was approximately 70% of the total body clearance ( CL tot : 10.8 ml/min/kg body wt), which was determined from the steady-state arterial plasma concentration and the infusion rate. These results indicated that the liver is the main organ responsible for the removal of [ 125 I]hEGF from the systemic circulation in rats. The renal extraction ratio ( E R ) of [ 125 I]hEGF was half of that of [ 14 C]inulin; this may have resulted from the plasma protein binding of [ 125 I]hEGF, which was approximately 50% as determined by the charcoal adsorption method and the equilibrium gel-filtration method. The renal clearance ( CL R : 2.65 ml/min/kg body wt), calculated by multiplying E R by the renal plasma flow rate ( Q PR ), was approximately 17% of the CL tot - (15.6 ml/min/kg body wt), indicating a minor contribution of CL R . to CL tot compared with that of CL H to CL tot . The CL R of [ 125 I]hEGF calculated from the urinary excretion data was one-tenth of that calculated from the plasma concentration difference between the femoral artery and the renal vein at steady state. These results suggest that the bulk of [ 125 I]hEGF cleared from the plasma by the kidney may have been metabolized further in the renal tubules before appearing in the urine.

In order to elucidate the factors affecting the hepatic transport of sulfobromophthalein (BSP) in a pathological condition, the kinetics of the disappearance of BSP from the blood and appearance in the bile were studied in rats chronically intoxicated with carbon tetrachlorde, and the importance of factors that might affect the kinetics, i.e. binding activites of plasma and hepatic cytoplasmic proteins, and glutathione S-transferase activity of Y-fraction, was examined. During chronic intoxication, although plasma protein albumin concentration decreased, no qualitative difference was shown in the high affinity binding site ( K 1 ). A significant decrease was shown in the cytoplasmic protein concentration for the Y- and Z-fractions in intoxicated rats; no significant difference was observed in the number of binding sites for both fractions, but their binding constants decreased. Glutathione S-transferase activity and glutathione (GSH) content were not altered, although a decrease in conjugating activity per rat was expected. The time course for the plasma disappearance and biliary excretion of BSP showed a remarkable delay after CCl 4 intoxication, while no difference was shown in the bile flow rate. It was concluded that hepatic blood flow might play a primary ro)e in the initial plasma disappearance of BSP and that the decrease in the Y-fraetion binding activity might explain the decrease in BSP uptake rate into the liver which was observed in intoxicated rats.

Hepatic transport of indocyanine green (ICG) and probable factors altering the disposition of ICG were examined in rats chronically intoxicated with carbon tetrachloride. Delays were shown in both plasma disappearance and biliary excretion of ICG in intoxicated rats. No significant difference was shown in the total amount of ICG bound to the plasma proteins. In the intoxicated rats, significant decreases were observed in the pharmacokinetic parameters, k 12 , k 34 and V 2 , calculated by a three-compartment model, while a significant increase was observed in k 21 ; V 1 was not altered. In both the control and intoxicated rats, the values of k 12 · V 1 were significantly smaller than the hepatic plasma flow, and it was suggested that the plasma flow does not play a primary role in the hepatic uptake of ICG. No significant difference was observed in the elution profiles of the 100,000 g supernatant fraction on a Sephadex G-75 column, and ICG bound mainly to the X-fraction in both the control and intoxicated rats. About 90 per cent of the ICG administered intravenously was distributed to the 9000 g precipitate fraction by 5 min in both groups of rats. It was concluded that a decrease in the permeability of the sinusoidal plasma membrane of the hepatocyte may explain the decrease of ICG uptake rate by the livers of the intoxicated rats.