Genetic markers can be used as instrumental variables, in an analogous way to randomization in a clinical trial, to estimate the causal relationship between a phenotype and an outcome variable. Our purpose is to extend the existing methods for such Mendelian randomization studies to the context of multiple genetic markers measured in multiple studies, based on the analysis of individual participant data. First, for a single genetic marker in one study, we show that the usual ratio of coefficients approach can be reformulated as a regression with heterogeneous error in the explanatory variable. This can be implemented using a Bayesian approach, which is next extended to include multiple genetic markers. We then propose a hierarchical model for undertaking a meta-analysis of multiple studies, in which it is not necessary that the same genetic markers are measured in each study. This provides an overall estimate of the causal relationship between the phenotype and the outcome, and an assessment of its heterogeneity across studies. As an example, we estimate the causal relationship of blood concentrations of C-reactive protein on fibrinogen levels using data from 11 studies. These methods provide a flexible framework for efficient estimation of causal relationships derived from multiple studies. Issues discussed include weak instrument bias, analysis of binary outcome data such as disease risk, missing genetic data, and the use of haplotypes. Copyright (c) 2010 John Wiley & Sons, Ltd.

ABSTRACT: INTRODUCTION: Recently an association between a genetic variation in TRAF1/C5 and mortality from sepsis or cancer was found in rheumatoid arthritis (RA). The most prevalent cause of death, cardiovascular disease, may have been missed in that study, since patients were enrolled at an advanced disease stage. Therefore, we used an inception cohort of RA patients to investigate the association between TRAF1/C5 and cardiovascular mortality, and replicate the findings on all-cause mortality. As TRAF1/C5 associated mortality may not be restricted to RA, we also studied a large cohort of non-RA patients. METHODS: 615 RA patients from the Leiden Early Arthritis Clinic (EAC) (mean follow-up 7.6 years) were genotyped for rs10818488. In addition 5634 persons enrolled in the PROspective Study of Pravastatin in the Elderly at Risk (mean follow-up 3.2 years) were genotyped for rs2416808 (R2 >0.99 with rs10818488). The life/death status was determined and for the deceased persons the cause of death was ascertained. Cox proportional hazards and regression models were used to assess hazard ratios (HR) and 95% confidence intervals (CI). RESULTS: Seventy-seven RA patients died. The main death causes in RA patients were cardiovascular diseases (37.7%), cancer (28.6%) and death due to infections (9.1%). No association was observed between the rs10818488 susceptible genotype AA and cardiovascular mortality (HR 1.08 95%CI 0.54 to 2.15) and all-cause mortality (HR 0.81 95%CI 0.27 to 2.43). Similar findings were observed for rs2416808 susceptible genotype GG in the non-RA cohort (HR 0.99; 95%CI 0.79 to 1.25 and HR 0.89; 95%CI 0.64 to 1.25, respectively). CONCLUSIONS: The TRAF1/C5 region is not associated with an increased mortality risk.

Pravachol and other statins have immune modulatory effects and have been shown to decrease the incidence of bronchiolitis obliterans (BrOb) in lung transplant recipients. It may also be useful in the treatment or prevention of hematopoietic stem cell transplant (HSCT) associated bronchiolitis obliterans. However, the safety of pravachol has not been shown in pediatric patients with BrOb after HSCT. We report on the safety and tolerability in 5 pediatric HSCT patients with established BrOb. All participants tolerated the drug without difficulty and there were no pravachol-associated adverse effects. Changes in creatine kinase (CK) and transaminases were minimal in 4 patients. One patient experienced increased CK and alanine aminotransferase, and a decrease in platelet count in the setting of severe systemic illness. No other patient had a clinically relevant change in white blood cell count, platelet count, or hemoglobin. Pravachol was well tolerated and safe in this group of patients, and merits further study in this patient population.

An 82-year-old woman was admitted to the hospital with dyspnea and fatigue. She had been given amlodipine, furosemide, candesartan, pravastatin and roxatidine acetate for two months in an other hospital. Chest CT showed patchy consolidations throughout the entire lungs. We suspected drug-induced pneumonia, and treated her with prednisolone under mechanical ventilation. The pulmonary consolidations eventually improved, but on the 15th hospital day the patient developed thrombocytopenia and disseminated intravascular coagulation (DIC). Heparin flushes had been performed since the first hospital day. After these were stopped, her platelet count became normal and the patient recovered from DIC. The clinical course, and the fact that testing for heparin-induced thrombocytopenia (HIT) antibodies was positive, supported the diagnosis of HIT and DIC. We report a rare case of HIT and DIC during treatment for drug-induced pneumonia.

Evidence accumulating from biological and epidemiological studies suggests that high levels of serum cholesterol may promote the pathological processes that lead to Alzheimer's disease (AD). Lowering cholesterol in experimental animal models slows the expression of Alzheimer's pathology. These findings raise the possibility that treating humans with cholesterol lowering medications might reduce the risk of developing AD or help treat it. The statins (lovastatin, pravastatin, simvastatin, and others) are powerful cholesterol lowering agents of proven benefit in vascular disease. Several clinical studies comparing the occurrence of AD between users and non-users of statins suggested that risk of AD was substantially reduced among the users. However, because these studies were not randomized trials, they provided insufficient evidence to recommend statin therapy. Cochrane reviews are based on the best available information about healthcare interventions and they focus primarily on randomized controlled trials (RCTs). On the issue of prevention, two randomized trials have been carried out and neither showed any reduction in occurrence of AD in patients treated with statins compared to those given placebo. Statins cannot therefore be recommended for the prevention of AD. Regarding treatment of AD, the large RCTs which have assessed this outcome have not published their results. Initial analysis from the studies available indicate statins have no benefit on the outcome measure ADAS-Cog but have a significant beneficial effect on MMSE as an outcome. We need to await full results from the RCTs before we can be certain. In addition statins were not detrimental to cognition in either systematic review.

OBJECTIVE: To review pitavastatin, the 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor and determine its place in the treatment of hypercholesterolemia. DATA SOURCES: Literature was accessed through PubMed (1948-December 2009). Pitavastatin, itavastatin, nisvastatin, NK 104, and NKS 104 were used as search terms. Results were limited to articles written in the English language. STUDY SELECTION AND DATA EXTRACTION: All articles identified from the data source were reviewed for inclusion. Articles included were those pertaining to the pharmacology and pharmacokinetic properties of pitavastatin, in addition to original research evaluating the clinical efficacy of pitavastatin for hypercholesterolemia. DATA SYNTHESIS: Pitavastatin is an oral HMG-CoA reductase inhibitor recently approved by the Food and Drug Administration for the treatment of primary hyperlipidemia and mixed dyslipidemia. Pitavastatin 2 mg has been shown to be noninferior to atorvastatin 10 mg and simvastatin 20 mg with respect to low-density lipoprotein cholesterol (LDL-C)-lowering ability. Additionally, pitavastatin 2 mg was shown in one study to lower LDL-C significantly more than pravastatin 10 mg. As with other HMG-CoA reductase inhibitors, primary safety concerns are related to myopathies and alterations in liver enzyme levels. While efficacy regarding beneficial effects on lipid parameters is comparable to that of other agents, a potential advantage of pitavastatin is its cytochrome P450 (CYP450) independent elimination, thereby reducing the likelihood of clinically significant drug-drug interactions. However, this is not a unique property, as pravastatin and rosuvastatin also possess this property. CONCLUSIONS: In light of the lack of outcome data, pitavastatin offers no clear advantage over other drugs in this class.

HMG-CoA reductase inhibitors (statins) can cause skeletal muscle toxicity; the risk of toxicity is elevated by drug interactions and pharmacogenetic factors that increase the concentration of statins in the plasma. Statins are substrates for several membrane transporters that may mediate drug interactions. Inhibitors of the organic anion transporting polypeptide 1B1 can decrease the hepatic uptake of many statins, as well as the therapeutic index of these agents. Potent inhibitors of cytochrome P450 (CYP)3A4 can significantly increase the plasma concentrations of the active forms of simvastatin, lovastatin and atorvastatin. Fluvastatin, which is metabolized by CYP2C9, is less prone to pharmacokinetic interactions, while pravastatin, rosuvastatin and pitavastatin are not susceptible to any CYP inhibition. An understanding of the mechanisms of statin interactions will help to minimize drug interactions and to develop statins that are less prone to adverse interactions.

Hepatocytes express various transporters in the sinusoidal and canalicular membrane, which mediate hepatic uptake and canalicular efflux, forming directional transport from the sinusoid to the bile. Drug-drug interactions and genetic polymorphisms of the transporters are known to cause variations in transporter function. This review focuses on pharmacokinetic modeling of hepatobiliary transport of drugs to explain the alteration of the disposition of drugs caused by such variations, based on the clearance concept. For modeling and simulation, pravastatin and dibromosulfophthalein have been used as model compounds which are known to undergo transpoter-mediated hepatic uptake followed by biliary excretion. Pharmacokinetic modeling of hepatobiliary transport illustrates the concept of the rate-determining process in overall hepatobiliary transport.

Inflammatory pathways are involved in the developement of atherosclerosis. Interaction of vessel wall cells and invading monocytes by cytokines may trigger local inflammatory processes. HMG-CoA reductase inhibitors (statins) are a standard medication used in cardiovascular diseases. They are thought to have anti-inflammatory capacities, in addition to their lipid-lowering effects. We investigated the anti-inflammatory effect of statins in the cytokine-mediated-interaction-model of human vascular smooth muscle cells (SMC) and human mononuclear cells (MNC). In this atherosclerosis-related inflammatory model LPS (lipopolysaccharide, endotoxin) as well as HMGB-1 stimulation resulted in synergistic (i.e., over-additive) IL-6 (interleukin-6) production as measured in ELISA. Recombinant IL-1, TNF-alpha and IL-6 mediated the synergistic IL-6 production. The standard anti-inflammatory drugs aspirin and indomethacin reduced the synergistic IL-6 production by 60%. Simvastatin, atorvastatin, fluvastatin, or pravastatin reduced the IL-6 production by 53, 50, 64, and 60%, respectively. The inhibition by the statins was dose-dependent. Combination of statins with aspirin and/or indomethacin resulted in complete inhibition of the synergistic IL-6 production. The same inhibitors blocked STAT3 phosphorylation, providing evidence for an autocrine role of IL-6 in the synergism. MNC from volunteers after five day aspirin or simvastatin administration showed no decreased IL-6 production, probably due to drug removal during MNC isolation. Taken together, the data show that anti-inflammatory functions (of statins) can be sensitively and reproducably determined in this novel SMC/MNC coculture model. These data implicate that statins have the capacity to affect atherosclerosis by regulating cytokine-mediated innate inflammatory pathways in the vessel wall.

There are insufficient data available on the efficacy and safety of lipid-lowering therapy for patients with dyslipidaemia complicated by multiple metabolic abnormalities. This study aimed to examine the efficacy and safety of ezetimibe 10 mg/day administered to Japanese patients with dyslipidaemia. This was a prospective study carried out at Kyushu University Hospital, Fukuoka, Japan. In one group, ezetimibe 10 mg/day alone was given to 33 patients for 12 weeks. In the other two groups, ezetimibe was given with an HMG-CoA reductase inhibitor (statin) to 13 patients for 12 weeks: pravastatin 10 mg/day (n = 7) or rosuvastatin 2.5 mg/day (n = 6). The main outcome measure was the effect of ezetimibe on low-density lipoprotein cholesterol (LDL-C) and other lipid levels from baseline to 12 weeks. After 12 weeks of treatment, all groups showed marked reductions in mean +/- SD LDL-C level (from 155.4 +/- 22.0 mg/dL at baseline to 118.0 +/- 28.1 mg/dL, i.e. -37.4 mg/dL; p < 0.001). The mean reduction in LDL-C level with ezetimibe monotherapy was significantly greater in patients with impaired LDL-C metabolism, glucose metabolism or hypertension than in those without such abnormalities (-21.0% vs -8.4%, p < 0.01; -22.7% vs -9.5%, p < 0.05; and -22.5% vs -5.9%, p < 0.05; respectively). The reduction in LDL-C levels with ezetimibe monotherapy was also correlated with the number of metabolic abnormalities (rho = 0.426, p = 0.013). Both ezetimibe monotherapy and combination therapy with ezetimibe and a statin were able to safely and effectively control LDL-C levels in Japanese patients with dyslipidaemia, including those with metabolic abnormalities.

Aim: The long-term effect of statin therapy in diabetic patients after coronary revascularization is not well established. Accordingly, we sought to determine if whether statin therapy initiated at the time of complete revascularization including percutaneous coronary intervention (PCI) and/or bypass surgery reduces total and cardiac mortality among diabetic patients.Methods: We collected data from 1,138 consecutive patients who underwent complete revascularization (PCI and/or bypass surgery). We then compared all-cause and cardiac mortality rates in 499 patients with diabetes mellitus of whom 149 (29.9%) were treated with statin at the time of revascularization. To adjust the variables that would have been related to the decision regarding statin administration, a propensity score was computed and multivariate Cox regression was carried out.Results: During follow-up (8.8+/-2.6 years), 103 patients died (including 43 who died of cardiac causes). The Multivariate analysis showed statin therapy to be significantly associated with reduced cardiac mortality (HR 0.39, 0.16-0.95; p=0.039), but not with all-cause mortality.Conclusion: Statin therapy was associated with a significantly reduced risk of cardiac mortality in patients with diabetes mellitus and coronary artery disease after complete revascularization.

Reactive oxygen species (ROS) are important intracellular signaling molecules and are implicated in cardioprotective pathways including ischemic preconditioning. Statins have been shown to have cardioprotective effects against ischemia/reperfusion injury, however, the precise mechanisms remain to be elucidated. We hypothesized that ROS-mediated signaling cascade may be involved in pravastatin-induced cardioprotection. Cultured rat cardiomyocytes were exposed to H(2)O(2) for 30 min to induce cell injury. Pravastatin significantly suppressed H(2)O(2)-induced cell death evaluated by propidium iodide staining and the MTT assay. Incubation with pravastatin activated catalase, and prevented a ROS burst induced by H(2)O(2), which preserved mitochondrial membrane potential. Protective effects were induced very rapidly within 10 min, which was concordant with the up-regulation of phosphorylated ERK1/2. L-NAME, 5HD, N-acetylcysteine (NAC) and staurosporine inhibited ERK1/2 phosphorylation and also reduced pravastatin-induced cardioprotection, suggesting NO, mitochondrial K(ATP) (mitoK(ATP)) channels, ROS and PKC should be involved in the cardioprotective signaling. We also demonstrated that pravastatin moderately up-regulated ROS generation in a 5HD-inhibitable manner. In isolated perfused rat heart experiments, pravastatin administered 10 min prior to no-flow global ischemia significantly improved left ventricular functional recovery, and also reduced infarct size, which were attenuated by the treatment with NAC, 5HD, L-NAME or staurosporine. Administration of pravastatin from the beginning of reperfusion also conferred cardioprotection. Pravastatin protected the cardiomyocytes against oxidative stress by preventing the ROS burst and preserving mitochondrial function. Moderately up-regulated ROS production by mitoK(ATP) channels opening is involved in the pro-survival signaling cascade activated by pravastatin.

LDL-apheresis (LDLa) efficacy in the treatment of symptomatic HyperLp(a)lipoproteinemia -HyperLp(a)- has been studied in a multicentre trial. After 3.1+/-2.7 years of weekly and biweekly treatment, the data from 19 patients (males:12; females:7; aged 53.8+/-9.3 years; mean body mass index: 24.6+/-2.3 Kg/m(2)) were evaluated. Data were collected using the same questionnaire shared by 5 participating centres. A total of 2331 procedures were performed. A mean of 3593.7+/-800.3 ml of plasma or 8115.3+/-2150.1 ml of blood, depending upon the technique used (H.E.L.P., D.A.LI., Dextransulphate, Lipocollect 200), was regularly treated on average every 10.1+/-2.6 days. Baseline mean Lp(a) levels were 172.3+/-153.8 mg/dL. The mean pre-/post-apheresis Lp(a) levels decreased from 124.5+/-107.2 mg/dL (p<0.001 vs baseline) to 34.2+/-40.6 mg/dL (p<0.001 vs pre-). Baseline mean LDL-cholesterol (LDLC) levels were 152.3+/-74.6 mg/dL. The mean pre-/post-apheresis LDLC levels decreased from 130.4+/-61.1 mg/dL (p<0.004 vs baseline) to 41.2+/-25.1 mg/dL (p<0.001 vs pre-). The hypolipidemic drugs given to the patients during LDLa were: ezetimibe+simvastatin, atorvastatin, rosuvastatin, pravastatin, acipimox, and omega-3 fatty acids. 58% of the patients had arterial hypertension. Cigarette smokers were 5.3%. Alcohol intake was present in 21%. 52.6% were physically active. Patients with coronary artery disease (CAD) submitted to coronary catheterization before LDLa were 95%. In 5.5% (#1) CAD recurred despite treatment with LDLa. 79% were submitted to coronary revascularization before LDLa. CAD was: monovasal in 8 patients (42.1%), bivasal in 5 (26.4%), trivasal in 4 (21%), plurivasal in 2 (10.5%). In 94.5% of the sample the lesions were stable (< 0% deviation) over 3.1+/-2.7 years. 37% had both CAD and extra-coronary artery disease. This multicentre study confirmed that long-term treatment with LDLa was at least able to stabilize CAD in the majority of the individuals with symptomatic HyperLp(a).

The major initiation process of intracranial aneurysms is thought to involve endothelial dysfunction due to hemodynamic stress. Angiotensin II type 1 receptor blockers and statins improve vascular endothelium function. The effects of olmesartan and pravastatin were investigated on the development of experimental aneurysms in rats. Eighty-three rats underwent aneurysm induction. Seven groups of 10-14 rats were treated with low or high dose olmesartan, low or high dose pravastatin, low doses of olmesartan and pravastatin, hydralazine, or no drug (control) for 12weeks, when rats were sacrificed for vascular corrosion casting and scanning electron microscopy. Aneurysmal changes at the anterior cerebral-olfactory artery bifurcation were divided into stages 0 (no abnormality) to III (saccular aneurysm). Systolic arterial blood pressure was elevated over 170mmHg in the control, low dose pravastatin, and high dose pravastatin groups, but not in the other groups. The control group demonstrated aneurysmal changes in 100% and stage III in 50% of rats. Aneurysmal changes were observed in most rats in the other groups, but the incidence of stage III was 10% or less. The staging pattern showed significant differences between the groups (P=0.028). Pravastatin reduced both stages III and II+III and olmesartan ameliorated stage III, implying that these may prevent aneurysmal formation through acting on different steps.

Background: Management of essential thrombocythemia (ET) in high-risk patients is difficult because high platelet numbers can lead to vascular occlusive events and bleeding. Therapeutic interventions in ET are limited to hydroxyurea and anagrelide; however, in Europe, anagrelide is contraindicated in patients with chronic renal disease. Objective: The aim of this case report was to describe the use of anagrelide in a patient with ET and renal impairment. Case summary: A 73-year-old white female patient with severe renal impairment who was diagnosed with ET was receiving treatment with hydroxyurea 1 g/d since 2001. At this time she was also receiving aspirin 80 mg/d; calcium carbonate 1 g/d; pravastatin 40 mg/d; folic acid 5 mg/d; furosemide 40 mg/d; cetirizine 10 mg/d; erythropoietin 10,000 U once monthly; a vitamin B complex, 1 tablet a day; and iron tablets 105 mg/d. In February 2007, because her white blood cell count fell to 2.1 x 10(9)/L, myelodepression was suspected and hydroxyurea was stopped. This led to enhanced platelet levels and the introduction of anagrelide at an initial dose of 0.5 mg/d that was steadily increased to 2.5 mg/d. All other treatments were continued with some dosage adjustments. Sodium bicarbonate 1 g/d and vitamin D were added to her regimen. After 18 months of anagrelide treatment, a sudden but moderate fall of platelets to 142 x 10(3)/muL with severe anemia (hemoglobin, 6.5 g/dL) was observed. The patient had anemia since 2004, but the condition worsened due to bleeding related to an ulcer at the cecal valve. The patient refused blood and platelet transfusions and surgical intervention for religious reasons. Because of hemodynamic instability, she was admitted to the intensive care unit in December 2008 and died 24 hours after admission. Conclusion: We report a case of ET and chronic renal failure treated with anagrelide and low-dose aspirin in a patient who did not receive transfusion and surgical intervention due to religious reasons, and had a fatal outcome.

PURPOSE: To evaluate whether initiation of a fibrate or statin increases the risk of hospitalization for gastrointestinal bleeding in warfarin users. METHODS: We used Medicaid claims data (1999-2003) to perform an observational case-control study nested within person-time exposed to warfarin in those > or =18 years (n=353,489). Gastrointestinal bleeding cases were matched to 50 controls based on index date and state. RESULTS: Chronic warfarin users had an increased odds ratio of gastrointestinal bleeding upon initiation of gemfibrozil (1.88; 95% confidence interval [CI], 1.00-3.54] for the first prescription; 1.75; 95% CI, 0.77-3.95 for the second prescription); simvastatin (1.46; 95% CI, 1.03-2.07 for the first prescription; 1.60; 95% CI, 1.07-2.39 for the second prescription); or atorvastatin (1.39; 95% CI, 1.07-1.81 for the first prescription; 1.05; 95% CI, 0.73-1.52 for the second prescription). In contrast, no increased risk was found with pravastatin initiation (0.75; 95% CI, 0.39-1.46 for the first prescription; 0.90; 95% CI, 0.43-1.91 for the second prescription). CONCLUSIONS: Initiation of a fibrate or statin that inhibits CYP3A4 enzymes, including atorvastatin, was associated with an increased risk of hospitalization for gastrointestinal bleeding. Initiation of pravastatin, which is mainly excreted unchanged, was not associated with an increased risk.

Currently, no consensus has been reached regarding the management of hyperlipidemia in patients who develop statin-associated myalgia (SAM). Many statin-intolerant patients use alternative lipid-lowering therapies, including red yeast rice. The present trial evaluated the tolerability of red yeast rice versus pravastatin in patients unable to tolerate other statins because of myalgia. The study was conducted in a community-based setting in Philadelphia, Pennsylvania. A total of 43 adults with dyslipidemia and a history of statin discontinuation because of myalgia were randomly assigned to red yeast rice 2,400 mg twice daily or pravastatin 20 mg twice daily for 12 weeks. All subjects were concomitantly enrolled in a 12-week therapeutic lifestyle change program. The primary outcomes included the incidence of treatment discontinuation because of myalgia and a daily pain severity score. The secondary outcomes were muscle strength and plasma lipids. The incidence of withdrawal from medication owing to myalgia was 5% (1 of 21) in the red yeast rice group and 9% (2 of 22) in the pravastatin group (p = 0.99). The mean pain severity did not differ significantly between the 2 groups. No difference was found in muscle strength between the 2 groups at week 4 (p = 0.61), week 8 (p = 0.81), or week 12 (p = 0.82). The low-density lipoprotein cholesterol level decreased 30% in the red yeast rice group and 27% in the pravastatin group. In conclusion, red yeast rice was tolerated as well as pravastatin and achieved a comparable reduction of low-density lipoprotein cholesterol in a population previously intolerant to statins.

Some investigations have looked into the ability of measurements of apolipoprotein B/apolipoprotein A-I (apoB/apoA-I) ratio to predict cardiovascular events. We hypothesized that a decrease in the apoB/apoA-1 ratio by statin therapy would act on suppression of coronary plaque progression. A 6-month prospective study was conducted of 64 patients with coronary artery disease treated with pravastatin. The plaque volume, assessed by volumetric intravascular ultrasonography, had decreased significantly by 12.6% (p <0.0001 vs baseline). Although a significant decrease of 6.4% and 14.6% was found in the serum level of apoB and the apoB/apoA-1 ratio (p = 0.0001 and p <0.0001, respectively, vs baseline), a significant increase of 14.0% of and 12.0% in the level of apoA-I and apoA-II (both p <0.0001 vs baseline). No significant changes were found in the level of apoC-II or apoE. A stepwise regression analysis revealed that the change in the apoB/apoA-1 ratio was an independent predictor of the change in coronary plaque volume (beta coefficient 0.386; p = 0.0023). In conclusion, our results have indicated that the decrease in the apoB/apoA-I ratio is a simple predictor for coronary atherosclerotic regression: the lower the apoB/apoA-I ratio, the lower the risk of coronary atherosclerosis.

Background and purpose: Organic anion transporting polypeptide 1B3 (OATP1B3) (SLCO1B3) mediates the uptake of endogenous substrates (e.g. estrone-3-sulphate) and drugs (e.g. pravastatin) from blood into hepatocytes. Structure-based modelling of OATP1B3 suggested that a pore with a positive electrostatic potential contributes to the transport mechanism. Therefore, we investigated the role of conserved positively charged amino acids for OATP1B3-mediated uptake of sulphobromophthalein (BSP) and pravastatin. Experimental approach: Residues Lys28, Lys41 and Arg580 in OATP1B3 were substituted by alanine, arginine, glutamine, glycine or lysine. Using immunofluorescence, immunoblot analysis and cellular uptake assays, the effect of these mutations on protein expression and transport activity was investigated. Key results: Immunofluorescence revealed that all mutants were localized in the plasma membrane with partial intracellular retention of the Arg580>Ala and Arg580>Lys mutants. Lys41>Ala, Lys41>Gln, Lys41>Gly, Arg580>Gly and Arg580>Lys showed significantly reduced transport for BSP and pravastatin. Kinetic analyses of BSP transport revealed a significant reduction of V(max) normalized to cell surface protein expression for Lys41>Ala (wild type: 190 +/- 8, Lys41>Ala:16 +/- 4 pmol (mg protein)(-1) min(-1), P < 0.001), whereas V(max) of Lys41>Arg and Arg580>Lys (103 +/- 8 and 123 +/- 14 pmol (mg protein)(-1) min(-1), P > 0.05) did not change significantly. This suggests that the positive charges at positions 41 and 580 are important for transport activity of BSP. Structural modelling indicated that the positively charged side chain of Lys41 is flexible within the pore. The orientation of Arg580 is defined by adjacent residues Glu74 and Asn77, which was confirmed by kinetic analysis of Glu74>Ala. Conclusions and implications: We demonstrated that the conserved positively charged amino acids Lys41 and Arg580 are pivotal to the transport activity of OATP1B3.