Akinori Urae

Polymorphisms of OATP-C (SLC21A6) and OAT3 (SLC22A8) genes: Consequences for pravastatin pharmacokinetics

Objective: Our objective was to quantitate the contribution of the genetic polymorphisms of the genes for 2 human organic anion transporters—organic anion transporting polypeptide C (OATP‐C) and organic anion transporter 3 (OAT3)—to the pharmacokinetics of pravastatin.

Long-term spatial cognitive impairment following middle cerebral artery occlusion in rats. A behavioral study.

Behavioral changes in the chronic phase of permanent occlusion of the right middle cerebral artery (MCA) in rats were investigated. One month after MCA occlusion, 23 rats were unable and 7 rats were able to solve a radial 8-arm maze task during a 1-month period. Three months after occlusion, 19 MCA-occluded rats failed to solve the task successfully again during at least a 1-month period (the cognitively impaired rats), and 11 MCA-occluded rats were able to solve it (the cognitively unimpaired rats). When a delay of 60 min was imposed for this task, five cognitively unimpaired rats failed to solve it. The locomotor activity of the cognitively impaired rats increased significantly 2 months after occlusion, and this increase showed good correlation with spatial cognitive deficit. However, the mean time a rat spent at each arm remained unchanged among the cognitively impaired, unimpaired, and sham-operated rats. There was no significant difference in the ratio between the cognitively impaired and unimpaired rats for disturbed motor coordination. These results suggest that MCA occlusion is capable of producing long-term spatial cognitive disturbance in rats. In addition, this spatial cognitive deficit does not seem to be primarily due to hypermotility or a disturbance in motor coordination.

Long-Term Spatial Cognitive Impairment after Middle Cerebral Artery Occlusion in Rats: No Involvement of the Hippocampus

The behavioral and neurochemical changes in the chronic phase of permanent occlusion of the right middle cerebral artery (MCA) in rats were investigated. One month after MCA occlusion, 23 rats were unable to solve a radial eight-arm maze task during an entire 1-month period, whereas seven rats were able to solve this task. Three months after occlusion, 19 MCA-occluded rats failed to solve the task successfully again for at least 1 month (the cognitively impaired rats), whereas 11 MCA-occluded rats were able to solve it (the cognitively unimpaired rats). The rats that underwent behavioral testing were examined for any changes in the acetylcholine (ACh) levels in the hippocampus using HPLC with electrochemical detection or the formation of long-term potentiation (LTP) in the population spike of the hippocampal CA1 field. The immunohistochemical distribution of either the microtubule-associated protein 2 (MAP2) or glial fibrillary acidic protein (GFAP) in the hippocampus of the cognitively impaired rats was also studied. In the cognitively impaired rats, neither the suppression of the induction of LTP, nor the degradation of MAP2, nor the increase in the GFAP immunoreactivity was observed in the hippocampus. The levels of ACh in the hippocampus did not change significantly among the cognitively impaired, unimpaired, and the sham-operated rats. These results suggest that MCA occlusion is capable of producing long-term spatial cognitive disturbance in rats without any evidence of neurobiological damage in the hippocampus.

Pharmacokinetics and pharmacodynamics of insulin aspart, a rapid-acting analog of human insulin, in healthy Japanese volunteers.

Pharmacokinetic and pharmacodynamic properties of a rapid-acting analog of human insulin, insulin aspart, were compared with those of soluble human insulin in Japanese healthy subjects. Subcutaneous single injections (0.025 and 0.05 U/kg body weight (BW)) of insulin aspart produced a significantly earlier peak of exogenous insulin level in comparison with human insulin (30.8+/-13.8 versus 61.3+/-14. 6 min, P<0.9001 for 0.025 U/kg; and 39.2+/-18.8 versus 99.2+/-53.8 min, P<0.005 for 0.05 U/kg). The peak serum level of insulin aspart was higher than that of human insulin (23.0+/-6.0 versus 9.9+/-3.1 microU/ml for 0.025 U/kg; and 30.9+/-9.2 versus 13.3+/-4.1 microU/ml for 0.05 U/kg, P<0.0001). The time to the minimal level of glucose after insulin aspart was significantly shorter compared with human insulin (P<0.05 for 0.025 U/kg BW and P<0.01 for 0.05 U/kg BW). The Delta change in blood glucose induced by insulin aspart was larger than that observed for human insulin at any dose (P<0.001). The repeated injection of insulin aspart before each meal also resulted in a rapid rise in exogenous insulin level with peak level obtained approximately 40 min after insulin aspart at any dose. When compared with results of other trials with insulin aspart, the present results showed that pharmacokinetic and pharmacodynamic profiles of the rapid-acting analog insulin aspart in Japanese subjects are no different from those in nonJapanese subjects.

Interaction magnitude, pharmacokinetics and pharmacodynamics of ticlopidine in relation to CYP2C19 genotypic status

Objectives The aim of this study was to investigate the impact of CYP2C19 polymorphism on the extent of the interaction and on the pharmacokinetics and pharmacodynamics of ticlopidine. Methods Homozygous (hmEMs) and heterozygous extensive metabolizers (htEMs), and poor metabolizers (PMs, n=6 each) took an oral dose (20 mg) of omeprazole. After a 1-week washout period, each subject received ticlopidine (200 mg) for 8 days, and ticlopidine pharmacokinetics were studied on days 1 and 7. On day 8, omeprazole was given again and its kinetic disposition was compared with that in the first dose. ADP-induced platelet aggregation was measured as a pharmacodynamic index. Results In contrast to the PMs, whose mean kinetic parameters were not altered by the repeated dosings of ticlopidine, an eight- to 10-fold increase in the mean AUC ratio of omeprazole to 5-hydroxyomeprazole was observed in both the EM groups. No significant intergenotypic differences in the pharmacokinetic parameters of ticlopidine were observed, although the accumulation ratio tended to be greater in hmEMs than in PMs (2.4±0.2 versus 1.7±0.2). A significantly positive correlation (P=0.031) was observed between the individual percent inhibition of platelet aggregation and AUC0–24 of ticlopidine regardless of the CYP2C19 polymorphism. Conclusions Ticlopidine is a potent inhibitor for CYP2C19 and may be associated with the phenocopy when CYPC19 substrates are co-administered to EMs. Whether and to what extent CYP2C19 would be involved in the metabolism of ticlopidine remain unanswered from the present in-vivo study.

The facilitating and suppressing effects of Δ9-tetrahydrocannabinol on the rise in intrasynaptosomal Ca2+ concentration in rats

The effects of delta 9-tetrahydrocannabinol (delta 9-THC) on the rise in intracellular Ca2+ concentrations ([Ca2+]i) after stimulation with 15 mM or 29 mM K+ in rat whole brain synaptosomes were examined. A fluorescent chelating agent, Rhod-2, was employed to monitor any alterations of K(+)-evoked [Ca2+]i. Pretreatment with 10(-10) M delta 9-THC for 3 min enhanced K(+)-evoked [Ca2+]i significantly, while 10(-9), 10(-8) or 5 x 10(-8) M delta 9-THC significantly inhibited the K(+)-evoked [Ca2+]i. These results suggest that delta 9-THC had a biphasic effect on the K(+)-evoked Ca2+ response in rat brain synaptosomes.

Kinetic analysis of the disposition of insulin-like growth factor 1 in healthy volunteers

AbstractPurpose. Insulin-like growth factor 1 (IGF-1) is predominantly bound to its specific binding proteins (IGFBPs) in circulating plasma. In the present study, pharmacokinetic analysis of IGF-1 was performed in healthy volunteers to characterize the effect of interactions with IGFBPs on IGF-1 disposition. Methods. Plasma concentration profiles of both free and bound IGF-1 were examined at several doses. An in vitro plasma protein binding was also analyzed. Results. The total body clearance (CLtotal) for the free IGF-1 was much higher than the creatinine clearance, suggesting that the major elimination pathway is by a route other than renal glomerular filtration. The CLtotal for the free IGF-1 exhibited a dose-dependent reduction whereas that for the sum of unbound and bound IGF-1 increased on increasing the dose. The data obtained fitted closely a one-compartment model that involved the binding and dissociation of IGF-1, as well as its biosynthesis and elimination. The estimated parameters suggest that IGF-1 exhibits high affinity binding to IGFBPs, the rate-limiting step in the overall elimination being the dissociation from IGFBPs. Conclusions. The saturation of both the plasma protein binding and elimination accounts for the nonlinear pharmacokinetic profile. The binding to IGFBPs markedly limits both the distribution and elimination of IGF-1.

No Effect of High-Protein Food on the Stereoselective Bioavailability and Pharmacokinetics of Verapamil

The effects of high‐protein food on the bioavailability of both the racemate and individual enantiomers of verapamil were investigated in 12 healthy volunteers using a randomized crossover design. Food had no effect on any parameter of bioavailability for both the racemate and the individual enantiomers of verapamil except time to maximum concentration (tmax), which was significantly prolonged after food intake. The pharmacokinetics of the enantiomers of norverapamil were not significantly changed by food intake. These results suggest that high‐protein food does not alter the pharmacokinetics and bioavailability of either the racemate or the individual enantiomers of verapamil. Therefore, the clinical efficacy of verapamil is not related to food intake, except for a slight prolongation in the time to onset of the pharmacologic effects. The present data can be applied to the high‐protein content meal intake.

Influence of cilnidipine or nisoldipine on sympathetic activity in healthy male subjects

The aim of this study was to investigate whether cilnidipine, an N- and L-type calcium channel blocker, and nisoldipine, an L-type calcium channel blocker, have different effects on sympathetic activity, using an identical group of healthy male subjects. Eight healthy men (22–28 years) were given 10 mg of cilnidipine or 10 mg of nisoldipine in a randomized crossover design. In each trial, in subjects without medication on day 1 (control) and with medication on day 2, we measured heart rate (HR), low frequency (LF)/high frequency (HF) of HR variability, and plasma noradrenaline (NA) in a resting supine position and during head-up tilt, and palmar sweating during a mental arithmetic test, before and at 1, 2, 4, 6, and 8 h after administration. Time-plasma concentration profiles of the two drugs were similar. Measurements in controls on the two days showed no significant difference in any of these parameters. Nisoldipine, but not cilnidipine, slightly increased HR and LF/HF at rest. Head-up tilt increased HR, LF/HF, and plasma NA. As evaluated with repeated-measures analysis of variance, head-up tilt induced a significant increase in LF/HF, but not HR or plasma NA, and the effect of cilnidipine was significantly less than that of nisoldipine (P = 0.017). Postural hypotension was not observed. There was no difference in mental arithmetic-induced sweating between the two drugs. Cilnidipine, but not nisoldipine, might have a weak inhibitory effect on reflex sympathetic activity.

Pepstatin A induces extracellular acidification distinct from aspartic protease inhibition in microglial cell lines.

The extrusion of protons is considered a very general parameter of the activation of many kinds of membrane or intracellular molecules, such as receptors, ion channels, and enzymes. We found that pepstatin A caused a reproducible, concentration‐related increase in the extracellular acidification rate in two microglial cell lines, Ra2 and 6‐3. Washing abolished pepstatin A‐induced acidification immediately. However, pepstatin A did not cause the extracellular acidification in other cell types, such as CHO, C6 glioma, and NIH3T3 cells. These observations strongly suggest that pepstatin A interacts with certain membrane proteins specific to both Ra2 and 6‐3 cells from outside. N‐methylmaleimide and N,N′‐dicyclohexylcarbodiimide, inhibitors of H+‐ATPase, were found to reduce pepstatin A‐induced response strongly, while bafilomycin A1, a vacuolar H+‐ATPase inhibitor, vanadate, a P‐type H+‐ATPase inhibitor, and NaN3, an F1 ATPase inhibitor, virtually did not. 5‐(N‐ethyl‐N‐isopropyl) amiloride, an inhibitor of Na+/H+ exchanger isoform 1, greatly enhanced pepstatin‐induced response, while amiloride did not. Zn2+, a voltage‐dependent proton channel blocker, did not affect pepstatin‐induced response neither. Staurosporine, a nonspecific inhibitor of protein kinase C, inhibited pepstatin A‐induced response, while chelerythrine, more selective inhibitor of protein kinase C, greatly enhanced it. H‐7 and H‐8 did not affected the response. These findings suggest that pepstatin A induces extracellular acidification in microglia cell lines, Ra2 and 6‐3, through an N‐methylmaleimide‐ and N,N′‐dicyclohexylcarbodiimide‐sensitive, but bafilomycin A1‐insensitive, ATPase, which seems to be distinct from protein kinase C‐dependent process.