Emerging diabetes therapies: Bringing back the ß-cells.

BACKGROUND: Stem cell therapies are finally coming of age as a viable alternative to pancreatic islet transplantation for the treatment of insulin-dependent diabetes. Several clinical trials using human embryonic stem cell (hESC)-derived ß-like cells are currently underway, with encouraging preliminary results. Remaining challenges notwithstanding, these strategies are widely expected to reduce our reliance on human isolated islets for transplantation procedures, making cell therapies available to millions of diabetic patients. At the same time, advances in our understanding of pancreatic cell plasticity and the molecular mechanisms behind ß-cell replication and regeneration have spawned a multitude of translational efforts aimed at inducing ß-cell replenishment in situ through pharmacological means, thus circumventing the need for transplantation. SCOPE OF REVIEW: We discuss here the current state of the art in hESC transplantation, as well as the parallel quest to discover agents capable of either preserving the residual mass of ß-cells or inducing their proliferation, transdifferentiation or differentiation from progenitor cells. MAJOR CONCLUSIONS: Stem cell-based replacement therapies in the mold of islet transplantation are already around the corner, but a permanent cure for type 1 diabetes will likely require the endogenous regeneration of ß-cells aided by interventions to restore the immune balance. The promise of current research avenues and a strong pipeline of clinical trials designed to tackle these challenges bode well for the realization of this goal.

Recommendations for workforce development in regenerative medicine biomanufacturing.

In its 2019 report, The Skilled Technical Workforce: Crafting America's Science and Engineering Enterprise, the National Science Board recommended a national charge to create a skilled technical workforce (STW) driven by science and engineering. The RegenMed Development Organization (ReMDO), through its RegeneratOR Workforce Development Initiative, has taken on this challenge beginning with an assessment of regenerative medicine (RM) biomanufacturing knowledge, skills, and abilities (KSAs) needed for successful employment. While STW often refers only to associate degree or other prebaccalaureate prepared technicians, the RM biomanufacturing survey included responses related to baccalaureate prepared technicians. Three levels of preparation were articulated in the research: basic employability skills, core bioscience skills, and RM biomanufacturing technical skills. The first two of these skill levels have been defined by previous research and are generally accepted as foundational-the Common Employability Skills developed by the National Network of Business and Industry Associations and the Core Skill Standards for Bioscience Technicians developed by the National Center for the Biotechnology Workforce. Fifteen skill sets addressing the specialized needs of RM and related biotechnology sectors were identified in the ReMDO survey, defining a third level of KSAs needed for entry-level employment in RM biomanufacturing. The purpose of the article is to outline the KSAs necessary for RM biomanufacturing, quantify the skills gap that currently exists between skills required by employers and those acquired by employees and available in the labor market, and make recommendations for the application of these findings.

Effect of the Aß aggregation modulator MRZ-99030 on retinal damage in an animal model of glaucoma.

Several lines of evidence suggest that there are similarities in the pathomechanisms of glaucoma and Alzheimer's disease, and that amyloid-beta (Aß) could be a new, promising target for neuroprotective therapy of glaucoma. In the present study, we evaluated the effect of the Aß aggregation modulator MRZ-99030 in the Morrison model of glaucoma based on increased intraocular pressure (IOP) in rats. MRZ-99030 provided dose-dependent neuroprotection and at the highest dose (240 mg/kg) reduced the degree of RGC apoptosis to 33 % of that seen after vehicle (P < 0.05; one-way ANOVA). No significant effect on IOP was observed. Pharmacokinetic experiments showed that following systemic injection of MRZ-99030, concentrations above affinity for Aß were reached. Hence the present results are consistent with the notion that Aß is a promising target for neuroprotective intervention in glaucoma and that MRZ-99030 may be a good drug candidate for further development.

The dopamine reuptake inhibitor MRZ-9547 increases progressive ratio responding in rats.

Drugs that are able to shift effort-related decision making in intact rats towards high-effort response options are largely unknown. Here, we examined the effects of two candidate drugs, MRZ-9547 and its l-enantiomer MRZ-9546 on progressive ratio (PR) responding using two different tasks, a standard PR task that involves increasing ratio requirements and a PR/chow feeding choice task in which animals can lever press for preferred food pellets under a PR schedule or approach freely available less preferred lab chow. Furthermore, we assessed the mechanisms of action of both drugs using in vitro-assay methods and in vivo-microdialysis. Results reveal that MRZ-9547 is a selective dopamine transporter (DAT) inhibitor that moderately stimulated striatal dopamine release. MRZ-9546 was a much less potent DAT inhibitor. Furthermore, MRZ-9547 dose dependently increased the tendency to work for food reinforcement both in the standard PR task and the PR/chow feeding choice task, MRZ-9546 was considerably less active. Relative to MRZ-9547, other DAT-interfering drugs had only moderate (methylphenidate) or marginal (modafinil, d-amphetamine) stimulant effects on PR responding in either task. Collectively, our data demonstrate that the DAT inhibitor MRZ-9547 can markedly stimulate PR responding and shift effort-related decision making in intact rats towards high-effort response options. An analysis of effort-related decision making in rodents could provide an animal model for motivational dysfunctions related to effort expenditure such as fatigue, e.g. in Parkinson's disease or major depression. Our findings suggest that DAT inhibitors such as MRZ-9547 could be potentially useful for treating energy-related symptoms in neurological or neuropsychiatric disorders.

Prevalence and treatment strategies of dyskinesia in patients with Parkinson's disease.

A study into the prevalence and treatment of dyskinesia in Parkinson's disease (PD) patients was performed with 380 PD specialists' completed interviews relating to PD and retrospectively completed 1900 patient record forms for patients with dyskinesia. Physicians reported, that 34% of their PD patients experience dyskinesia, 57% of dyskinetic PD patients were affected by moderately-to-completely disabling dyskinesia. Treatment of dyskinesia was looked upon as not satisfactory, fractionating of levodopa dose was used as first choice therapeutic option of dyskinesia.

[Dyskinesia in Parkinson's disease--major clinical features, aetiology, therapy]. / Dyskinesien bei Morbus Parkinson--Klinik, Atiologie, Therapie.

Parkinson's disease (PD), a slowly, progressive degenerative disorder of the central nervous system, which affects about ten million people world-wide, is currently treated symptomatically. Current treatment aim i. e. to balance the decreased dopamine turnover in striatal neurons. Chronic exposure to dopaminergic agents, however, supports onset of motor complications and dyskinesia in the long term. Dyskinesia appear mainly as chorea, athetosis, dystonia, stereotypia, ballism or a combination. Sometimes excessive abnormal facial, body and limb movements depend on the overall dosage of dopaminergic substitution. This is why the main therapy is based on reducing the total dosage of dopaminergic substances. Either alternative or additional well-tried substances like apomorphine, amantadine or clozapine are used. New possibilities in treatment emerge from substances like sarizotan, istradefylline, fipampezol or talampanel. Even so disability and reduced quality of life in PD patients and their caregivers may exist. This survey describes the major clinical features, aetiology and demographics of treatment-associated dyskinesia in PD.

Altered vascular remodeling in fibulin-5-deficient mice reveals a role of fibulin-5 in smooth muscle cell proliferation and migration.

Fibulin (fbln)-5 is an elastin-binding protein required for assembly and organization of elastic fibers. To examine the potential role of fbln-5 in vascular remodeling and neointima formation, we induced vascular injury by carotid artery ligation in fbln-5(-/-) mice. Mutant mice displayed an exaggerated vascular remodeling response that was accompanied by severe neointima formation with thickened adventitia. These abnormalities were not observed in elastin(+/-) mice that exhibited a comparable reduction of vessel extensibility to fbln-5(-/-) mice. Thus, the severe remodeling response could not be attributed to altered extensibility of the vessel wall alone. Vascular smooth muscle cells cultured from fbln-5(-/-) mice displayed enhanced proliferative and migratory responses to mitogenic stimulation relative to wild-type cells, and these responses were inhibited by overexpression of fbln-5. These findings demonstrate the importance of the elastic laminae in vascular injury, and reveal an unexpected role of fbln-5 as an inhibitor of vascular smooth muscle cell proliferation and migration.

Subchronic effects of olanzapine on sleep EEG in schizophrenic patients with predominantly negative symptoms.

BACKGROUND: It is well known that sleep disturbance is an integral symptom of schizophrenia. In recent studies, a deficit of delta sleep has been observed in schizophrenic patients. Antipsychotic drugs with serotonin (5-HT2) receptor-antagonistic properties are considered to have delta sleep promoting effects. We have investigated the effects of subchronic olanzapine treatment on sleep EEG in schizophrenic patients. METHODS: The effects of administration of olanzapine (15 to 20 mg) on sleep were studied for four weeks in 10 male, drug-free patients suffering from schizophrenia with predominantly negative symptoms. Conventional sleep EEG parameters were investigated at baseline and after treatment with olanzapine for four weeks. Additionally, spectral power analysis of the EEG signal in distinct frequency bands was computed for different sleep stages. Psychopathology (PANSS, HAMD-17, HAMA) and side effects were assessed weekly. RESULTS: All patients improved, as measured by PANSS global scores. Compared to baseline, there was a significant improvement of parameters of sleep efficiency and an increase of delta sleep as well as REM sleep. Regarding spectral power values, no significant differences between baseline and treatment conditions were found. CONCLUSIONS: Sleep improvement was due to parameters of sleep efficiency and delta sleep, which may be related to serotonin antagonistic properties of olanzapine.

Sarizotan, a serotonin 5-HT1A receptor agonist and dopamine receptor ligand. 1. Neurochemical profile.

Sarizotan exhibited high affinities only to serotonin 5-HT1A receptors and dopamine DA D4>D3>D2 receptors with the profile of a 5-HT1A agonist and DA antagonist demonstrated by the inhibition of cAMP-stimulation and guinea pig ileum contraction, decreased accumulation of the 5-HT precursor 5-hydroxytryptophan and increased levels of 5-HT metabolites, increased accumulation of DA precursor dihydroxyphenylalanine (DOPA) and the reduced levels of DA metabolites in intact rats. However, sarizotan at higher doses decreased DA precursor accumulation in reserpinized rats and induced contralateral rotational behavior in unilaterally substantia nigra lesioned rats, indicating some intrinsic dopaminergic activity; at D2 receptors sarizotan may act as a partial agonist, depending on the dopaminergic impulse flow. Sarizotan represents a new approach for the treatment of extrapyramidal motor complications such as l-DOPA-induced dyskinesia in Parkinson's disease.

Repeated rating improves value of diagnostic dopaminergic challenge tests in Parkinson's disease.

Clinicians use acute challenges with levodopa (LD) and/or apomorphine (A) for diagnostic dopaminergic response tests in Parkinson's disease (PD) patients. We consecutively compared the value of both drugs with performance of repeated ratings and adverse effect recording. Oral administration of 200 mg LD was superior to subcutaneous injection of 4 mg A in terms of tolerability and onset of temporary UPDRS motor score decline ([previously untreated PD patients] LD: 4.02 [mean] +/- 2.45 [SD] [significant decrease: p = 1.42 E-07] vs. A: 1.58 +/- 3.38 [not significant decrease: p = 0.14], p = 0.0009; [treated PD patients] LD: 7.71 +/- 4.35 [significant decrease: p = 2.48 E-06] vs. A: 5.19 +/- 4.32 [significant decrease: p = 7.83 E-05], p = 0.07). We suggest diagnostic acute challenge test performance with LD as first- and A as second choice due to better tolerability and valuation in combination with repeated scoring procedures to improve sensitivity and specifity.

Retinal nerve fibre layer loss in patients with type 1 diabetes mellitus without retinopathy.

BACKGROUND/AIM: There is evidence suggesting the occurrence of neurovisual abnormalities in patients with diabetes without retinopathy. However, the determination of abnormalities in the neural and glial elements in vivo is difficult. The aim of this study was to investigate whether a retinal nerve fibre layer (RNFL) defect (as determined by scanning laser polarimetry, SLP) is present in patients without clinical manifestations of diabetic retinopathy. METHODS: 12 patients with type 1 diabetes mellitus (DM) without retinopathy or other diabetes induced microvascular complications, underwent a complete ophthalmological examination, including automated perimetry and RNFL measurements with a nerve fibre layer analyser GDx. The data were compared with a normal control group matched for age and sex. RESULTS: The superior segment retardation in patients with diabetes was lower than in the control group, based on the superior integral (0.19 (SD 0.06) v 0.23 (0.04) mm(2), p=0.03) and the superior average (71.0 (11.05) v 84.27 (10.56) microm, p=0.007) parameters. CONCLUSION: This finding may be indicative of significant nerve fibre loss in the superior segment of the retina in patients with type 1 diabetes mellitus but without retinopathy. The meaning of intraretinal differences in RNFL retardation, indicating asymmetric NFL loss, in patients with diabetes is yet not understood.

Detection of tolcapone in the cerebrospinal fluid of parkinsonian subjects.

The cerebral availability of the peripherally and centrally acting catechol-O-methyltransferase (COMT) inhibitor tolcapone is not known in humans. Therefore, we determined the concentration of tolcapone in cerebrospinal fluid (CSF) of 12 parkinsonian subjects 1-4 h after oral application of 200 mg of the drug. The mean concentration was 56.4+/-35.5 nmol/l (mean +/- SD). This concentration was calculated to cause 75.2+/-15% (mean +/- SD) inhibition of COMT in CSF. Thus, tolcapone efficiently inhibits COMT after crossing the blood-brain barrier in humans.

1,1'-Diisopropyl-2,4'-cyanine (disprocynium24), a potent uptake2 blocker, inhibits the renal excretion of catecholamines.

1,1'-Diisopropyl-2,4'-cyanine (disprocynium24), a potent inhibitor of the extraneuronal monoamine transport system (uptake2), was previously shown to reduce the clearance of catecholamines from plasma not only by blocking uptake2 but presumably also by blocking organic cation transport. To provide more direct evidence for the latter conclusion, the present study was carried out in anaesthetized rabbits. It aimed at determining the effect of disprocynium24 on the renal excretion of catecholamines which is known to be, at least in part, a consequence of organic cation transport in the kidney. To this end, the plasma clearance due to renal excretion (Cl(u)) of endogenous as well as infused 3H-labelled adrenaline, noradrenaline and dopamine was determined for 60-min periods of urine collection in rabbits treated either with disprocynium24 (270 nmol kg(-1) i.v. followed by i.v. infusion of 80 nmol kg(-1) min(-1)) or vehicle. Two groups of animals were studied: group I (monoamine oxidase and catechol-O-methyltransferase intact) and group II (monoamine oxidase and catechol-O-methyltransferase inhibited). A third group of animals with intact monoamine oxidase and catechol-O-methyltransferase was used to study the effect of disprocynium24 on the glomerular filtration rate (as determined by measuring the plasma clearance of inulin). In vehicle controls, Cl(u) of endogenous adrenaline, noradrenaline and dopamine was 7.2, 5.2 and 153.6 ml kg(-1) min(-1), respectively, in group I and 10.4, 7.0 and 134.3 ml kg(-1) min(-1), respectively, in group II. Similar control values of Cl(u) were obtained for infused 3H-adrenaline and 3H-noradrenaline, but not for infused 3H-dopamine; Cl(u) of 3H-dopamine (4.9 ml kg(-1) min(-1) in group I and 15.4 ml kg(-1) min(-1) in group II) was considerably smaller than Cl(u) of endogenous dopamine, indicating that most of the dopamine in urine (i.e., 98% in group I and 92% in group II) was derived from the kidneys rather than from the circulation. By contrast, only about one quarter of the noradrenaline in urine (32% in group I and 24% in group II) and none of the urinary adrenaline were of renal origin. In both groups, disprocynium24 markedly reduced the Cl(u) of endogenous catecholamines (by 72-90%) and of infused 3H-catecholamines (by 49-69%). Moreover, it preferentially inhibited the renal excretion of those components of urinary dopamine and noradrenaline which were derived from the kidney. Therefore, disprocynium24 inhibits the tubular secretion of catecholamines and, hence, organic cation transport in the kidney. This conclusion was substantiated by the observation that disprocynium24 did not alter the glomerular filtration rate.

Disprocynium24 induces a dopamine-independent, eukaliuric diuresis and natriuresis in the anaesthetized rat.

In the anaesthetized rat, intravenous administration of the isocyanine 1,1'-diisopropyl-2,4'-cyanine (disprocynium24) at doses up to 600 microg/kg resulted in marked diuresis and natriuresis without affecting urinary potassium excretion. Fractional sodium excretion was increased over 10-fold indicating a high ceiling-diuretic action. The effects of disprocynium24 on renal function were accompanied by a dose-dependent reduction in heart rate (HR) and mean arterial blood pressure (MAP). Acute administration of 600 microg/kg disprocynium24 decreased MAP by 25% and, in addition, caused a fall in glomerular filtration rate (GFR). Since i) disprocynium24 has been shown to interfere with urinary dopamine excretion (UDAV) and ii) dopamine has been implicated with the regulation of renal sodium excretion, we hypothesized that the effects of disprocynium24 might be mediated by its effects on renal dopamine handling. The following findings, however, argue against this hypothesis. First, administration of disprocynium24 in single doses up to 600 microg/kg caused a diuresis and natriuresis, but did not significantly affect U(DA)V. Second, neither the systemic nor the renal response to disprocynium24 were markedly altered by pretreatment with the dopamine D1- or D2-receptor blockers SCH23390 (10 microg x kg(-1) x min[-1]) or S(-)sulpiride (15 microg x kg(-1) x min[-1]), respectively.

Disprocynium24, a novel inhibitor of the extraneuronal monoamine transporter, has potent effects on the inactivation of circulating noradrenaline and adrenaline in conscious rat.

The role of extraneuronal uptake in terminating the actions of catecholamines has been difficult to evaluate in vivo, largely because of lack of suitable inhibitors. The compound, 1,1'-diisopropyl-2,4'-cyanine iodide or disprocynium24 (D24), is a novel inhibitor of extraneuronal uptake with a high degree of potency in vitro. This study examined the actions of D24 on the inactivation and metabolism of circulating noradrenaline and adrenaline in conscious rats. Animals received i.v. infusions of 3H-labelled noradrenaline and adrenaline, and their extraneuronal O-methylated metabolites, normetanephrine and metanephrine. Plasma concentrations of endogeneous and 3H-labelled catecholamines and metanephrines were measured before and after D24. D24 caused large increases in plasma concentrations of noradrenaline and adrenaline, effects due to both decreases in their plasma clearances and increases in their rates of release into plasma. Plasma concentrations of normetanephrine and metanephrine also increased due to their decreased clearance from plasma. Increased release of normetanephrine into plasma did not contribute to increased plasma concentrations of normetanephrine. In fact, the contribution of extraneuronal O-methylation to noradrenaline clearance decreased substantially after D24. The data indicate that D24 is a potent inhibitor of the extraneuronal catecholamine transporter in vivo and that this process contributes importantly to the removal of circulating catecholamines and their O-methylated amine metabolites. Increased release of noradrenaline into plasma may reflect an increase in the proportion of transmitter that escapes from sites of release into the circulation. However, increased adrenaline release indicates that the drug also causes sympathoadrenal activation.

Pharmacokinetic and alpha 1-adrenoceptor antagonistic properties of two cyanine-type inhibitors of extraneuronal monoamine transport.

1,1'-Diethyl-2,2'-cyanine (decynium22) and 1,1'-diisopropyl-2,4'-cyanine (disprocynium24) are highly potent inhibitors of the extraneuronal monamine transporter. When given as i.v. bolus injections (4 mumol kg-1) to anaesthetized rabbits, both drugs elicited a transient fall in blood pressure without altering heart rate. The observed maximum fall in diastolic blood pressure was 59% after decynium22 and 43% after disprocynium24 administration. The pharmacokinetics of decynium22 and disprocynium24 were similar; they were characterized by short half-lives for elimination (8.2 and 4.5 min, respectively) and very high plasma clearances (173 and 180 ml kg-1 min-1, respectively). The mechanism underlying the blood pressure-lowering effect of decynium22 was explored in the isolated incubated rabbit aorta. Decynium22 antagonized the noradrenaline-induced contraction; the pA2 for this interaction was 7.6, and the slope of the corresponding Schild plot was unity. In a membrane preparation from rat myocardium, decynium22 as well as disprocynium24 inhibited the specific binding of [125I]-2-[beta-(4-hydroxy-3-iodophenyl)-ethylaminomethyl]- tetralone (125I-HEAT), a selective ligand to alpha 1-adrenoceptors. The Ki's were 5.3 and 240 mumol l-1 for decynium22 and disprocynium24, respectively. The type of binding inhibition by decynium22 was competitive. It is concluded that the two inhibitors of extraneuronal monoamine transport decynium22 and disprocynium24 lower blood pressure by blocking alpha 1-adrenoceptors. A comparison of their potencies in blocking extraneuronal monoamine transport and alpha 1-adrenoceptors clearly indicates that disprocynium24 is more suitable for studies designed to determine the role of extraneuronal monoamine transport in vivo. Considering its very fast elimination kinetics, disprocynium24 must be administered by constant rate-infusions in order to avoid large fluctuations of plasma levels.

The role of extraneuronal amine transport systems for the removal of extracellular catecholamines in the rabbit.

As selective inhibitors of the extraneuronal monoamine uptake system (uptake2) suitable for in-vivo studies were not available, the question of whether uptake2 plays a definite role in vivo is largely unresolved. We attempted to resolve the question by using 1,1'-diisopropyl-2,4'-cyanine iodide (disprocynium24), a novel agent that blocks uptake2 in vitro with high potency. Anaesthetized rabbits were infused with 3H-labelled noradrenaline, adrenaline and dopamine, and catecholamine plasma clearances as well as rates of spillover of endogenous catecholamines into plasma were measured before and during treatment with either disprocynium24 or vehicle. Four groups of animals were studied: group I, no further treatment: group II, monoamine oxidase (MAO) and catechol-O-methyltransferase (COMT) inhibited; group III, neuronal uptake (uptake1) inhibited; group IV, uptake1 as well as MAO and COMT inhibited. Disprocynium24 (270 nmol kg-1 i.v. followed by an i.v. infusion of 80 nmol kg-1 min-1) did not alter heart rate and mean arterial blood pressure, but increased cardiac output by 22% and decreased the total peripheral vascular resistance by 16% with no difference between groups. When compared with vehicle controls, catecholamine clearances (normalized for the cardiac output of plasma) were decreased and spillover rates increased in response to disprocynium24. Although there were statistically significant between-group differences in baseline clearances (which decreased in the order: group I > group II > group III > group IV), the drug-induced clearance reductions relative to vehicle controls were similar in groups I to IV and amounted to 29-38% for noradrenaline, 22-31% for adrenaline and 16-22% for dopamine. Hence, there was still a significant % reduction in catecholamine clearances even after the combined inhibition of MAO and COMT, and there was no increase in the % reduction of clearances after inhibition of uptake1. Noradrenaline spillover increased in response to disprocynium24 in all four groups by 1.6- to 1.9-fold, whereas a 1.5- to 2.0-fold increase in adrenaline and dopamine spillover was observed in groups II and IV only. The results indicate that disprocynium24 interferes with the removal of circulating catecholamines not only by inhibiting uptake2, but also by inhibiting related organic cation transporters. As disprocynium24 increased the spillover of endogenous catecholamines into plasma even after inhibition of MAO and COMT, organic cation transporters may also be involved in the removal of endogenous catecholamines before they enter the circulation.

Transport of small organic cations in the rat liver. The role of the organic cation transporter OCT1.

The kidneys and the liver are the principal organs for the inactivation of circulating organic cations. Recently, an organic cation transporter (OCT1) has been cloned from rat kidney. In order to answer the question whether OCT1 is involved also in hepatic uptake of organic cations, the pharmacological characteristics of organic cation transport in hepatocytes were compared to the characteristics of transiently expressed OCT1. Primary cultures of rat hepatocytes avidly accumulated the small organic cation 3H-1-methyl-4-phenylpyridinium (3H-MPP+). At equilibrium, the hepatocytes accumulated 3H-MPP+ 56-fold. Initial rates of specific 3H-MPP+ transport in hepatocytes were saturable. The half-saturating concentration was 13 mumol/l. 3H-MPP+ transport was sensitive to quinine (Ki = 0.79 mumol/l) and cyanine863 (Ki = 0.097 mumol/l). Quinine and cyanine863 are known inhibitors of type I hepatic transport of cationic drugs and of renal excretion of organic cations, respectively. To compare the functional characteristics of 3H-MPP+ transport in hepatocytes with those of OCT1, OCT1 has been heterologously expressed and characterized in a mammalian cell line (293 cells). Initial rates of 3H-MPP+ transport were saturable, the Km being 13 mumol/l. The rank order of inhibitory potencies of various inhibitors was almost identical in hepatocytes and 293 cells transiently transfected with OCT1. There was a positive correlation between the Ki's for the inhibition of 3H-MPP+ transport in isolated hepatocytes and transfected 293 cells (r = 0.85; P < 0.01; n = 8). The results indicate that OCT1 is functionally expressed not only in the kidney but also in hepatocytes where it is responsible for the transport of small organic cations which, in the past, have been classified as type I substrates.