Safety and efficacy of low-dose PI3K inhibitor taselisib in adult patients with CLOVES and Klippel-Trenaunay syndrome (KTS): the TOTEM trial, a phase 1/2 multicenter, open-label, single-arm study

PURPOSE

PIK3CA pathogenic variants in the PIK3CA-related overgrowth spectrum (PROS) activate phosphoinositide 3-kinase signaling, providing a rationale for targeted therapy, but no drug has proven efficacy and safety in this population. Our aim was to establish the six-month tolerability and efficacy of low-dose taselisib, a selective class I PI3K inhibitor, in PROS patients.

METHODS

Patients over 16 years with PROS and PIK3CA pathogenic variants were included in a phase IB/IIA multicenter, open-label single-arm trial (six patients at 1 mg/day of taselisib, then 24 at 2 mg/day). The primary outcome was the occurrence of dose limiting toxicity (DLT). Efficacy outcomes were the relative changes after treatment of (1) tissue volume at affected and unaffected sites, both clinically and on imaging; (2) cutaneous vascular outcomes when relevant; (3) biologic parameters; (4) quality of life; and (5) patient-reported outcomes.

RESULTS

Among 19 enrolled patients, 2 experienced a DLT (enteritis and pachymeningitis) leading to early trial termination (17 treated, 10 completed the study). No serious adverse reaction occurred in the 1 mg cohort (n = 6). No significant reduction in affected tissue volume was observed (mean -4.2%; p = 0.81; SD 14.01). Thirteen (76.4%) participants reported clinical improvement (pain reduction, chronic bleeding resolution, functional improvement).

CONCLUSION

Despite functional improvement, the safety profile of low-dose taselisib precludes its long-term use.

Model reduction of genome-scale metabolic models as a basis for targeted kinetic models

Constraint-based, genome-scale metabolic models are an essential tool to guide metabolic engineering. However, they lack the detail and time dimension that kinetic models with enzyme dynamics offer. Model reduction can be used to bridge the gap between the two methods and allow for the integration of kinetic models into the Design-Built-Test-Learn cycle. Here we show that these reduced size models can be representative of the dynamics of the original model and demonstrate the automated generation and parameterisation of such models. Using these minimal models of metabolism could allow for further exploration of dynamic responses in metabolic networks.

Mesocarp of Brazil nut (Bertholletia excelsa) as inspiration for new impact resistant materials

Aiming to produce bioinspired impact and puncture resistant materials, the mesocarp of the Brazil nut (Bertholletia excelsa) was characterized. The mesocarp composition was investigated by chemical extraction and its microstructure was analyzed by optical microscopy and microtomography (microCT). A compression test evaluated the force needed to open the mesocarp shell. Shore D hardness testing and nanoindentation measured the local mechanical properties at different length scales. Brazil nut mesocarp has a higher content of lignin (56%) than other nutshells and is mainly composed of sclereids and fibers cells arranged together and not in separated layers as usually found in nature. The mesocarp has an internal and external layer with fibers oriented from peduncle to opercular opening and a middle layer where entangled fibers are latitudinally oriented. To open a Brazil nut mesocarp, compression forces of 10 079  ±  1460 N (parallel to latitudinal section) and 14 785  ±  4050 N (perpendicular to latitudinal section) are needed. Such forces are higher than the forces needed to open most nutshells, if fracture force is normalized by shell thickness. The Shore D hardness test showed that hardness is uniform in the mesocarp, although it is higher in the center of the thickness than close to the inner or outer surface. The cell wall of fibers has a higher reduced modulus than the cell wall of sclereids although they have a similar hardness. These microstructural and mechanical results indicate that Brazil nutshell has great potential as a source for bioinspiration and motivates further studies.

Biomimetic cellular metals-using hierarchical structuring for energy absorption

Fruit walls as well as nut and seed shells typically perform a multitude of functions. One of the biologically most important functions consists in the direct or indirect protection of the seeds from mechanical damage or other negative environmental influences. This qualifies such biological structures as role models for the development of new materials and components that protect commodities and/or persons from damage caused for example by impacts due to rough handling or crashes. We were able to show how the mechanical properties of metal foam based components can be improved by altering their structure on various hierarchical levels inspired by features and principles important for the impact and/or puncture resistance of the biological role models, rather than by tuning the properties of the bulk material. For this various investigation methods have been established which combine mechanical testing with different imaging methods, as well as with in situ and ex situ mechanical testing methods. Different structural hierarchies especially important for the mechanical deformation and failure behaviour of the biological role models, pomelo fruit (Citrus maxima) and Macadamia integrifolia, were identified. They were abstracted and transferred into corresponding structural principles and thus hierarchically structured bio-inspired metal foams have been designed. A production route for metal based bio-inspired structures by investment casting was successfully established. This allows the production of complex and reliable structures, by implementing and combining different hierarchical structural elements found in the biological concept generators, such as strut design and integration of fibres, as well as by minimising casting defects. To evaluate the structural effects, similar investigation methods and mechanical tests were applied to both the biological role models and the metallic foams. As a result an even deeper quantitative understanding of the form-structure-function relationship of the biological concept generators as well as the bio-inspired metal foams was achieved, on deeper hierarchical levels and overarching different levels.

Influence of cell-to-cell variability on spatial pattern formation

Many spatial patterns in biology arise through differentiation of selected cells within a tissue, which is regulated by a genetic network. This is specified by its structure, parameterisation and the noise on its components and reactions. The latter, in particular, is not well examined because it is rather difficult to trace. The authors use suitable local mathematical measures based on the Voronoi diagram of experimentally determined positions of epidermal plant hairs (trichomes) to examine the variability or noise in pattern formation. Although trichome initiation is a highly regulated process, the authors show that the experimentally observed trichome pattern is substantially disturbed by cell-to-cell variations. Using computer simulations, they find that the rates concerning the availability of the protein complex that triggers trichome formation plays a significant role in noise-induced variations of the pattern. The focus on the effects of cell noise yields further insights into pattern formation of trichomes. The authors expect that similar strategies can contribute to the understanding of other differentiation processes by elucidating the role of naturally occurring fluctuations in the concentration of cellular components or their properties.

Molecular combination of the dopamine and serotonin scaffolds yield in novel antipsychotic drug candidates - characterization by in vivo experiments

Serotonin and dopamine play an important role in the aetiology of schizophrenia. Combination of the structural scaffolds of both neurotransmitters in a single molecule lead to aromatic [d,g]-bisannelated azecine derivatives, which have been shown to be nanomolar to subnanomolar dopamine D1-D5 receptor antagonists with a preference for the D1 family. In this work the potential antipsychotic activity of some azecine derivatives was predicted by their dopamine receptor affinities obtained in vitro from radioligand binding experiments and conclusively confirmed in vivo (rats) by applying a conditioned avoidance model. Furthermore, the compounds were tested in vivo for the development of catalepsy, which is a predictive parameter for extra-pyramidal side-effects caused by many antipsychotics. The investigated azecines displayed low cytotoxicity, and the affinities for human dopamine D1-D5 and serotonin 5-HT2 A receptors were in a nanomolar range. In vivo, their antipsychotic activities in the rat model were comparable with those of haloperidol and risperidone, but revealed a 2-5 times better therapeutic range with regard to catalepsy. Preliminary tests for oral bioavailability also revealed promising results for this new class of potential antipsychotic compounds. In conclusion, our in vivo experiments show that aromatic [d,g]-annelated azecines represent a novel and advantageous class of potential atypical neuroleptics.

Monoclinic phase transformations of zirconia-based dental prostheses, induced by clinically practised surface manipulations

Full-ceramic zirconia crowns and bridges have become very popular with dentists and patients because of their excellent esthetics and mechanical properties. We studied phase transformations within the outermost surface layer of 3 mol.% yttria-stabilized zirconia (Y-TZP) samples of small, clinically relevant thicknesses, manipulated by polishing, grinding and fracture as might be encountered in everyday clinical practice. Stress-induced transformations of the tetragonal phase were studied in three dimensions in order to better understand the organization and extent of the monoclinically transformed phase. By means of laboratory- and synchrotron-based X-ray diffraction measurements, coupled with electron microscopy and multimodal tomography, it was possible for the first time to visualize and quantify the phase distributions non-destructively and in three dimensions. Highly variable degrees of local transformation result in ragged transformed zones of very inhomogeneous thickness. The overall thickness of the transformation layers strongly depends on the severity and rate of loading. Gentle diamond cutting resulted in surprisingly low transformation ratios of less than 0.1%. When Y-TZP constructions are manipulated before bonding, toughness of the outer layers is reduced and they may become brittle with important implications for the stability of the bond: dental practitioners thus need to be cautious when altering the surfaces of these materials after sintering.

Modelling polar auxin transport in developmental patterning

Auxin interacts with its own polar transport to influence cell polarity and tissue patterning. Research over the past decade has started to deliver new insights into the molecular mechanisms that drive and regulate polar auxin transport. The most prominent auxin efflux protein, PIN1, has subsequently become a crucial component of auxin transport models because it is now known to direct auxin flow and maintain local auxin gradients. Recent molecular and genetic experiments have allowed the formulation of conceptual models that are able to interpret the role of (i) auxin, (ii) its transport, and (iii) the dynamics of PIN1 in generating temporal and spatial patterns. Here we review the current mathematical models of patterning in two specific developmental contexts: lateral shoot and vein formation, focusing on how these models can help to untangle the details of auxin transport-mediated patterning.

Efforts to establish an animal model of Fanconi syndrome after ifosfamide administration to rats

About 10% of children develop Fanconi syndrome (FS) a few months after ifosfamide (IFO) treatment. To establish an animal model, IFO was injected as 4 or 5 treatment courses (TCs, once daily for 3 consecutive days), to adult female rats (AF, 8 mg 100 g(-1) body wt, 4 TCs), to young female rats (YF, 8 mg 100 g(-1) body wt, 5 TCs) and to male rats (M, 6 mg 100 g(-1) body wt, 4 TCs). In the adult female rats, polyuria with electrolyte and albumin wasting occurred acutely, 2 days after the first treatment course. After the third treatment course, 30% of the rats died, but survivors showed a reduced excretion of electrolytes and glucose. The body weight increase was significantly diminished in adult female and male rats by about 25% or 70%, respectively. Up to 5 months after 5 TCs in young female rats, 15% of the animals died but the survivors did not show any sign of renal failure. In males, 28% of the rats died and in surviving animals the excretion of electrolytes, proteins and glucose as well as GFR were reduced 7 weeks after the last treatment course. There were no pathomorphological changes in kidney and liver. Determination of renal and hepatic cytochrome P450 activities indicated that results of adult female and male rats could be caused by starving, known as a common side effect of IFO, and not by its nephrotoxicity. Altogether, it was not possible to establish a model of a Fanconi syndrome persisting after cessation of IFO treatment in our rat strain, whereas acute, FS-like IFO effects on the kidney could be shown.

In vivo investigations on the cholinesterase-inhibiting effects of tricyclic quinazolinimines: Scopolamine-induced cognitive impairments in rats are attenuated at low dosage and reinforced at higher dosage

Tricyclic quinazolinimines as a novel class of potent inhibitors of cholinesterases in vitro are micro- and sub-micromolar inhibitors with activities at both acetyl- (AChE) and butyrylcholinesterase (BChE) or at BChE only. To further establish the antiamnesic properties of this class of compounds, an in vivo test system has been established. Cognitive impairment in rats was reversibly induced by scopolamine (0.05 mg/100 g body weight) and evaluated in an eight-arm radial maze. A representative quinazolinimine (MD212) showed attenuation of cognitive deficits at a low dosage (0.01 mg/100 g body weight), whereas at a high dosage (>0.1 mg/100 g body weight) the effect of scopolamine is markedly reinforced. As MD212 applied alone does not influence rat's cognition at all, the reinforcement of scopolamine effect has to be due to the amplification of scopolamine action possibly by (1) inhibition of scopolamine metabolism, (2) influence of scopolamine on MD212 metabolism or (3) allosteric modulation of mACh receptors. Receptor-binding studies proved hypothesis (3): MD212 stabilizes [3H]N-methylscopolamine binding to muscarinic receptors allosterically.

[In vitro investigations of phase I metabolism of the fomocaine derivative Oe 9000 with pig liver homogenates]

2,2'-[4-(4-Phenoxymethylphenyl)butylimino]diethanol (Oe 9000) is a new, highly potent local anaesthetic related to fomocaine. It displays a long duration of action, low toxicity and is superior to fomocaine with regard to aqueous solubility and efficacy. In view of the development of new application forms, e.g. for the treatment of postoperative pain, the elucidation of the biotransformation of the drug is required. Therefore, experiments with 10000 x g supernatants and microsomes from pig liver homogenates were conducted. Using specifically synthesized reference compounds six phase I metabolites could be identified by LC-MS. Apart from the predominating oxidative desamination of the compound, that led after redox reactions to the corresponding butyric acid and butanol derivatives, oxygenation of the exocycle, oxidative N-desalkylation, and N-oxidation were observed. Thus, with the exception of one compound only metabolites are generated, that are expected to have no local anaesthetic activity due to their reduced basicity.

Asymmetrical (ADMA) and symmetrical dimethylarginine (SDMA) as potential risk factors for cardiovascular and renal outcome in chronic kidney disease - possible candidates for paradoxical epidemiology?

BACKGROUND

Asymmetrical dimethylarginine (ADMA) is an inhibitor of nitric-oxide synthase. It has been linked to atherosclerotic risk in the general population as well as in end-stage renal disease patients (ESRD), whereas symmetrical dimethylarginine (SDMA) is thought to be biological inactive. Prospective data concerning the role of both dimethylarginines are rare in patients with chronic kidney disease.

METHODS

200 Patients with chronic kidney disease (mean age 57.6 +/- 13.0 years, 69 female, 131 male); 82 with chronic renal failure (CRF), 81 on maintenance haemodialysis (HD) and 37 renal transplant recipients (RTR) were prospectively followed for 24 months. ADMA and SDMA were measured by HPLC. The relation of plasma levels of ADMA and SDMA together with conventional risk factors for the cardiovascular and renal outcome was investigated with Cox proportional hazards model.

RESULTS

Mean serum levels of SDMA were significantly increased in all groups compared to the control group (P <or= 0.0005), ADMA was increased only in HD and RTR (P <or= 0.004). Forty-seven cardiovascular events (CVE) occurred during follow-up, 35 patients died, and 39 patients reached ESRD. Multivariate analysis showed diabetes (RR 3.072, P = 0.01), ESRD (RR 11.915, P < 0.0005), elevated CRP levels (RR 3.916, P < 0.0005) and surprisingly a lower ADMA level (RR 0.271, P = 0.008) as independent risk factors for CVE. Serum creatinine (RR 11.378, P = 0.001), haemoglobin (RR 0.710, P = 0.038 for an increment of 1 mmol/l), and SDMA levels (RR 1.633, P = 0.006, per 1 micromol/l increment) were predictors for the progression to ESRD.

CONCLUSIONS

Data from a heterogeneous group of patients with chronic kidney disease provide evidence that conventional risk factors seem to play a more important role than elevated serum levels of ADMA or SDMA for cardiovascular events. Increasing serum SDMA concentration seems to play an additive role for the renal outcome besides serum creatinine and haemoglobin levels. Whether ADMA might possibly be a candidate for the phenomenon of "paradoxical epidemiology" in chronic kidney disease needs further investigation.

In vitro investigations on the differential pro-oxidant and/or antioxidant properties of cyclosporin A and tacrolimus in human and rat liver microsomes

OBJECTIVE

The use of cyclosporin A (CSA) and tacrolimus (TAC) in organ transplantation and in the therapy of immune disorders is often hampered by adverse effects, mainly nephro-, hepato- and neurotoxicity. For the development of these side effects, among others, an increased formation of reactive oxygen species, probably generated by the cytochrome P450 (CYP) system, has been accused. Since in this respect literature data are inconsistent, in the present study possible pro- and/or antioxidant effects of CSA and TAC and the involvement of the CYP system were re-evaluated in vitro.

METHODS

Effects of CSA and TAC were examined on CYP mediated oxidase functions by stimulated lipid peroxidation (LPO), H2O2 production, and lucigenin (LC) or luminol (LM) amplified chemiluminescence (CL) in liver microsomes of either untreated rats or of rats treated with beta-naphthoflavone (BNF), phenobarbital (PB) or dexamethasone (DEX) and in human liver microsomes.

RESULTS

In rat liver microsomes, CSA displayed pro-oxidant properties (though only very slightly), whereas in human liver microsomes small antioxidant effects were seen. With TAC in both species the antioxidant capacity prevailed. Treatment of rats with BNF or DEX caused an increase in the pro-oxidant effects of CSA with respect to LPO or LM-CL, whereas in liver microsomes of DEX-treated rats H2O2 production and LC-CL were diminished.

CONCLUSIONS

CSA seems to have both pro-oxidant and antioxidant properties, whereas with TAC mainly an antioxidant capacity was seen. The CYP system seems to be involved in the pro-oxidant influence of CSA. Whether pro-oxidant or antioxidant effects predominate may depend on the antioxidant capacity of a tissue and on the CYP isoforms mainly present.

Effect of stress ratio on the fatigue behaviour of compact bone

During the fatigue process of bone, cracks generally initiate from the inherent defects existing in the bone. The fatigue lives of bone specimens at different stress levels as well as at different stress ratios R were evaluated using a computer simulation in which the crack propagation behaviour initiated from the inherent defects in the bone are herein considered. The S-N curves as well as the distributions of fatigue lives obtained by the simulations accurately conform with the experimental results. With the strain threshold epsilon(max) representing fatigue failure of the bone specimen, the values of 1500 microepsilon for R = -1, 2500 microepsilon for R = 0.1 and 4000 microepsilon for R = 10 were extrapolated from the simulations. These values conform with experimental values reported in the literature. Such conformity indicates that the strain threshold for fatigue failure is associated with the threshold value for crack propagation.

Effect of smoking on risk factors for cardiovascular disease in patients with diabetes mellitus and renal insufficiency

BACKGROUND

Many studies have been published demonstrating a strong correlation between smoking, renal lesions and cardiovascular morbidity and mortality. Possible contributing factors are elevated blood pressure values, changes in vascular reactivity, concentrations of lipids, fibrinogen and carboxyhemoglobin, in patients with diabetes mellitus, the quality of diabetes control and insulin resistance. Other possible risk factors may include advanced glycation end (AGE)-products, total plasma homocysteine and metabolites as well as symmetrical (SDMA) and asymmetrical (ADMA) dimethylarginine. It was the goal of the present trial to investigate the serum concentrations of these >new<, possible risk factors in a selection free population of patients with type 1 and insulin-treated type 2 diabetes mellitus, in patients with chronic renal insufficiency and in renal transplant recipients. The second aim was to analyse the effect of cigarette smoking on the levels of these laboratory parameters.

PATIENTS AND METHODS

A total of 544 subjects (n = 98 patients with chronic renal insufficiency without hemodialysis, n = 84 patients with hemodialysis, n = 50 renal transplant recipients, n = 114 patients with type 1 and n = 147 patients with insulin treated type 2 diabetes mellitus, n = 51 healthy controls) participated in the trial.

RESULTS

Patients with renal insufficiency had significantly higher concentrations of the AGE-products N-epsilon-Carboxymethyllysine (CML) and pentosidine compared with both groups of patients with insulin-treated diabetes mellitus and the healthy controls. In patients with type 1 diabetes there was a positive correlation between HbA1c and the concentration of CML (r = 0.405, p = 0.017) and between the pentosidine-concentration and the serum creatinine-level (r = 0.482, p = 0.001). In type 2 diabetes there was a correlation between CML and diastolic blood pressure (r = 0.239, p = 0.039). In comparison to the healthy controls, patients with renal diseases and patients after kidney transplantation had higher concentrations of total plasma homocysteine and its metabolites. Similar results were found for SDMA and ADMA: Patients with chronic renal insufficiency both with and without hemodialysis had significantly higher values than the renal transplant recipients and healthy controls. A clear influence of cigarette smoking on the levels of the laboratory parameters measured could not be determined in any group; neither in the patients with diabetes mellitus, nor in the patients with renal diseases, nor in the healthy controls.

CONCLUSIONS

The present trial demonstrates an increase in the parameters linked to the development of cardiovascular diseases including total plasma homocysteine, its metabolites, the dimethylarginines SDMA and ADMA and advanced glycation end-products depending on the degree of renal insufficiency. Moreover, in patients with insulin-treated diabetes mellitus, the concentrations of the AGE-products CML and pentosidine seem to be strongly influenced by the quality of diabetes control and blood pressure levels. There was no influence of cigarette smoking on the levels of the laboratory parameters measured.

Regulation of renal amino acid (AA) transport by hormones, drugs and xenobiotics - a review

Major advances have recently been made in our understanding of the mechanisms and functions of amino acid transport in mammalian cells: - from the whole organism to transporter molecular structure. In this article, we present a brief overview of current knowledge concerning amino acid transporters, followed by a detailed discussion of the relevance of this new information to our broader understanding of the physiological regulation of amino acid handling in the kidney. We focus especially on the influence of hormones and xenobiotics on renal amino acid transport systems. In a growing number of cases, it now seems possible to correlate the effects of hormones, drugs, and xenobiotics with the capacity of renal amino acid transporters. This topic is of clinical relevance for the treatment of many amino acid reabsorption disorders. For example, under suitable conditions glucocorticoids and thyroid hormones stimulate renal reabsorption of amino acids and might therefore be of benefit in the treatment of different kinds of aminoaciduria. Hormonal regulation also underlies the postnatal development of renal amino acid reabsorption capacity, which can be stimulated to mature earlier after exogenous administration of e.g. glucocorticoids. In contrast, many compounds (e.g. heavy metal complexes) selectively damage renal amino acid transporters resulting in urinary amino acid loss. These types of phenomena (stimulation or inhibition of amino acid transporters in the kidney) are reviewed from the perspectives of our new molecular understanding of transport processes and of clinical relevance.

Effects of arginine, L-alanyl-L-glutamine or taurine on neutrophil (PMN) free amino acid profiles and immune functions in vitro

The objective of this study was to determine the effects of arginine, L-alanyl-L-glutamine (Ala-Gln) or taurine on polymorphonuclear leucocyte (PMN) free amino acid profiles, superoxide anion (O2-) generation, hydrogen peroxide (H2O2) formation and released myeloperoxidase activity (MPO). Arginine led to significant increases in PMN arginine, ornithine, citrulline, aspartate, glutamate and alanine concentrations as well as increased H2O2-generation and MPO activity while O(2-)-formation was decreased. Ala-Gln caused significant increases in PMN free glutamine, alanine, asparagine, aspartate, glutamate, ornithine, arginine, serine and glycine concentrations and increased PMN immune functions. Taurine significantly increased PMN free taurine profiles, reduced PMN neutral amino acid content and decreased H2O2- and O(2-)-formation while MPO was increased. Altogether, the pharmacological regimens which enhance the supply of arginine, Ala-Gln or taurine in whole blood significantly affect PMN "susceptible free amino acid pool". This may be one of the determinants in PMN nutrition considerably influencing PMN immune functions. Introduction Polymorphonuclear leucocytes (PMN) ensure an important part of non-specific cell-mediated immunity and play a crucial role in the host defense

Ex vivo stimulation of renal transport of the cytostatic drugs methotrexate, cisplatin, topotecan (Hycamtin) and raltitrexed (Tomudex) by dexamethasone, T3 and EGF in intact human and rat kidney tissue and in human renal cell carcinoma

Previous experiments have shown that both in vivo and in vitro pre-treatment with various hormones increases the renal transport capacity for weak organic acids, such as PAH, in rats. The aim of the present study was to test whether or not accumulation of the anticancer drugs methotrexate (MTX), cisplatin (CP), raltitrexed (Tomudex) and topotecan (Hycamtin) can be increased in intact, healthy rat and human renal cortical slices and in human renal cell carcinoma (RCC). Intact, healthy human tissue was obtained from tumour bearing kidneys of patients suffering from RCC. Experiments were intended as a new approach to overcome so-called multidrug resistance. Kidney tissue slices were incubated for 24 h in William's medium E containing various concentrations of dexamethasone, T(3), or EGF. Thereafter slices were placed in anticancer drug containing Cross-Taggart medium and the drug uptake into kidney tissue was measured for 2 h. In intact rat and human renal tissue slices, the uptake of p-aminohippurate (PAH = reference substance) increased significantly after incubation in dexamethasone containing medium (134% and 156%, respectively). There were no stimulating effects of either T(3) or EGF on PAH accumulation. On the other hand, only the accumulation of MTX, but not of CP, raltitrexed or topotecan, was significantly enhanced after hormone pre-treatment both in intact renal tissue and in RCC. A stimulation of renal PAH accumulation can be performed ex vivo, as reported previously, both in intact rat and human renal cortical slices and in RCC. Discrepancies between the effects of dexamethasone and T(3) or EGF indicate different modes of action of these substances at the cellular level. Unfortunately, with the exception of MTX, the uptake of anticancer drugs can not be stimulated effectively ex vivo in human RCC tissue by the substances used. Evidently the transport of these anticancer drugs out of the kidney cells is more effective than their uptake.

Renal amino acid transport in immature and adult rats during chromate and cisplatinum-induced nephrotoxicity

The effects of sodium dichromate (chromate; 1 mg/100 g b. wt. s.c.) and cisdiamminedichloroplatinum(II) (CP; 0.6 mg/100 g b. wt. i. p.) on renal amino acid excretion and plasma amino acid composition were investigated in 10- and 55-day-old anaesthetised rats. On the basis of diuresis experiments on conscious rats the mentioned doses and times (1st day after chromate in both age groups and in 10-day-old rats after CP and 3rd day after CP in adult rats) were found out to be optimal for the characterisation of amino acid transport after heavy metal poisoning. Interestingly, in conscious 10-day-old rats chromate nephrotoxicity is not detectable after 1 mg/100 g b. wt. whereas all of the other experimental groups showed nephrotoxic effects of chromate and CP in conscious rats. Urine volumes are lower, but not significantly, in anaesthetised immature rats, independently of the administered nephrotoxin. But GFR is significantly lower in 10-day-old rats, both in controls and after CP, whereas after chromate GFR is significantly reduced only in adult rats and age differences disappeared. In principle the renal fractional excretion (FE) of amino acids was distinctly higher in immature rats as a sign of lower amino acid reabsorption capacity. Nevertheless, the amino acid plasma concentrations were relatively high in immature rats. However, both chromate and CP did not distinctly influence amino acid plasma concentrations. But in both age groups the administration of chromate and CP significantly decreased amino acid reabsorption capacity (increase in FE) as a sign of nephrotoxicity, most pronounced in adult rats after CP. The investigation of renal amino acid handling confirms (1) that both CP and chromate are nephrotoxins, (2) that CP was more nephrotoxic in 55-day-old animals compared to immature rats as could be demonstrated before using other parameters for nephrotoxicity testing and showed (3) that determination of renal amino acid handling is a highly sensitive marker for nephrotoxicity testing, especially in immature rats.

Temporary warm ischaemia, 5/6 nephrectomy and single uranyl nitrate administration--comparison of three models intended to cause renal fibrosis in rats

In patients the progression of pathologic renal processes after the treatment of primary disease is a problem of increasing importance and therapeutic strategies are insufficient till now. The aim of this paper was to search for rat models of interstitial fibrosis as a basis for testing therapeutic strategies to prevent end-stage renal failure. Experiments were done on adult female Wistar rats (Han:Wist) to investigate long-term consequences of temporary warm ischaemia, 5/6 nephrectomy (5/6 NX) and single uranyl nitrate (UN) administration (0.3 or 0.5 mg/ 100 g body wt. intraperitoneally). Observation time was 20 weeks after injury in each group. Creatinine clearance, urinary protein excretion and hydroxy-proline (OH-proline) concentration in renal tissue were measured and light microscopic investigations were done to characterise both quality and time course of long-term renal damage in relation to matched control animals. Temporary warm ischaemia and 5/6 NX did not cause any fibrotic changes during the 20 weeks observation period. The higher UN dose led to decreased creatinine clearance, increased urinary protein excretion and enhanced OH-proline concentration in renal tissue. Morphologic investigations showed fibrotic areas containing strongly dilated and atrophic tubules with thickened basal membranes. These effects can be seen from week four after UN administration up to the end of the observation period. In conclusion, administration of one single dose of UN is a simple procedure to induce interstitial renal fibrosis as an experimental model to investigate therapeutic strategies for their prevention.

Local anaesthetic effectivity and toxicity of fomocaine, five N-free fomocaine metabolites and two chiralic fomocaine derivatives in rats compared with procaine

Until now, no optimal local anaesthetic drug with long lasting effect and low toxicity has been developed. Fomocaine (CAS 17692-39-6), introduced in the German extrapharmacopoela (DAC) in 1979, is a local anaesthetic, which is largely in accordance with these aspects. Now the basic ether fomocaine, its metabolites O/Se 9 (CAS 3006-96-0), O/Se 10 (CAS 31719-76-3), O/Se 11, O/Se 12 (CAS 64264-21-7) and M5 and its chiralic derivatives O/G 3 and O/G 5 were compared with procaine (CAS 59-46-1) and characterised more in detail in rats. The metabolism of fomocaine was investigated earlier with 14C-fomocaine in rats and beagle dogs. Rac-O/G 3 and Rac-O/G 5 could be separated into the enantiomers via the diastereomeric salts. Basing on standard methods for the testing of the local anaesthetic effects (estimation of infiltration and conduction anaesthesia in rat tail, measurement of corneal anaesthesia) and using a couple of tests characterising the side effects and toxicity of local anaesthetic (paresis of the N. ischiadicus, tissue irritation, determination of the approximative i.p. LD50) it can be concluded that: a) The very good surface anaesthesia caused by fomocaine could be stated, but, as expected, concerning conduction anaesthesia, procaine is better qualified for clinical use. b) Fomocaine is much more effective in conduction and surface anaesthesia than its chiralic derivatives O/G 3 and O/G 5. c) Differences between the two enantiomers of the O/G-substances have been found, but these little discrepancies are without practical relevance. In the case of O/G 5, agonistic effects of both enantiomers could be shown. d) Fomocaine undergoes extensive biotransformation with subsequent formation of 14 metabolites. Five of them (O/Se 9-O/Se 12; M5) are N-free and do not show any pharmacological activity. e) Compared to other local anaesthetics, fomocaine is relatively non-toxic (nearly no tissue irritation, high approximative LD50), however, surprisingly the toxicity of the reference substance procaine has been found to be lower after i.p. administration instead of i.v. administration in comparison with fomocaine.

LLU-alpha, an endogenous metabolite of gamma-tocopherol, is more effective against metal nephrotoxicity in rats than gamma-tocopherol

Antioxidants of the vitamin E family have protective effects against metal toxicity. We examined the protective effect of racemic LLU-alpha [2,7,8-trimethyl-2-(carboxyethyl)-6-hydroxychroman] a metabolite of gamma-tocopherol, in comparison to the effect of alpha- and gamma-tocopherol in rats treated with sodium dichromate (Cr) or thallium sulfate (Tl). We measured metal nephrotoxicity based on urinary protein excretion and discussed it with respect to the metal concentration in renal tissue. The ranking of antioxidant activity (iron stimulated lipid peroxidation, luminol and lucigenin amplified chemiluminescence) was determined in the following order: alpha-tocopherol<gamma-tocopherol<LLU-alpha. Pretreatment with LLU-alpha produced lower chromate nephrotoxicity than alpha- or gamma-tocopherol, but did not influence Cr concentration in renal tissue. The protective effect of LLU-alpha against Cr toxicity seemed to be caused by its stronger antioxidant activity in comparison to alpha- and gamma-tocopherol. Pretreatment with LLU-alpha resulted in lower thallium-induced proteinuria, a lower concentration of Tl in the renal medulla, and higher urinary Tl excretion. Unlike LLU-alpha, which has been shown to inhibit K(+) channels in the apical membrane of the thick ascending limb of Henle's loop, we found that gamma-tocopherol did not. This finding reaffirmed the similarity between K(+) and Tl(+) and also explained the significantly decreased Tl concentration in the renal medulla in rats treated with LLU-alpha. We speculate that the protective effect of LLU-alpha against Tl nephrotoxicity is caused both by its antioxidant effect and, at least in part, by its ability to decrease Tl concentration as a consequence of inhibited Tl(+) uptake through K(+) channels. This finding confirmed the similarity between K(+) and Tl(+) and also explained the significantly decreased Tl concentration in the renal medulla in rats treated with LLU-alpha.

Counterion evaporation

We study the adsorption behavior of a highly charged rodlike polyelectrolyte approaching an oppositely charged planar wall in an unbounded electrolyte solution. The grand potential, the entropy, and the total number of screening particles are calculated as functions of the rod-wall distance, using input parameters that are typical of a DNA-molecule and charged lipid bilayers. It is found that counterions which are bound to the polyelectrolyte at infinite rod-wall distances will be released, or "evaporated," as the DNA molecule moves closer to the charged wall. This effect can be regarded as the opposite of the ion-condensation process. The transition of ions from the system of screening ions into the reservoir of bulk ions can lead to an increase of the enthalpy. This gain of enthalpy for the whole system manifests itself as an attractive contribution to the effective interaction between the wall and the polyelectrolyte.

Identification of the site of glucocorticoid action on neutral amino acid transport in superficial nephrons of rat kidney

Glucocorticoid hormones enhance the reabsorptive capacity of filtered amino acids in rat kidney, as it was shown in previous in vivo clearance experiments. In the present study, the site of glucocorticoid action on neutral amino acid transport in superficial nephrons of rat kidney was investigated using in vivo micropuncture technique. Adult female Wistar rats were treated with dexamethasone (DEX), and fractional excretion of L-glutamine (L-Gln) and L-leucine (L-Leu) were determined and related to inulin after microinfusion into different nephron segments. DEX reduced fractional excretion of both neutral amino acids as a sign of enhanced reabsorptive capacity. The site of main DEX action on L-Leu reabsorption has been localized in the proximal straight tubule. However, in the case of L-Gln, the inhibition of gamma-glutamyltranspeptidase (gamma-GT) by administration of acivicin indicated the importance of this brush border enzyme in reduced L-Gln excretion. DEX enhanced gamma-GT activity by tubular acidification. It can be presumed a DEX-inducible transport system for neutral amino acids mainly localized in proximal straight tubules of rat kidney.

Serum concentrations of asymmetric (ADMA) and symmetric (SDMA) dimethylarginine in renal failure patients

BACKGROUND

Nitric oxide (NO) synthesis is inhibited by the ADMA that accumulates in the plasma of patients with renal failure; however, the concentration of SDMA also is enhanced. Therefore, it has been hypothesized that ADMA and SDMA may contribute to hypertension in these patients.

METHODS

We measured the concentrations of ADMA, SDMA and 21 endogenous amino acids in 257 persons by high pressure liquid chromatography (HPLC).

RESULTS

The plasma concentrations of both ADMA and SDMA were significantly elevated in patients with chronic renal failure (CRF). The increase was more pronounced for SDMA (2.05 +/- 0.1 micromol/L vs. 0.5 +/- 0.04 micromol/L), whereas it was only moderate for ADMA (0.85 +/- 0.03 micromol/L vs. 0.73 +/- 0.06 micromol/L). In dialysis patients, the concentrations were further increased (ADMA, 1.05 +/- 0.04 micromol/L; SDMA, 2.68 +/- 0.13 micromol/L). After kidney transplantation, the concentration of SDMA returned to the baseline value (1.15 +/- 0.11 micromol/L), but that of ADMA remained enhanced (0.99 +/- 0.06 micromol/L).

CONCLUSIONS

In CRF, especially the concentration of SDMA is significantly increased. Not only ADMA, but also SDMA are likely to be responsible for hypertension. Competition for reabsorption between SDMA and arginine within the kidney has to be considered for the interpretation of changes in the ratio between dimethylarginines and arginine in renal failure. Hemodialysis is not suitable for a long-lasting removal of methylarginines. Whether the administration of arginine could have promising effects on hypertension and complications of CRF needs to be studied in prospective trials.

Homocysteine, its metabolites, and B-group vitamins in renal transplant patients

BACKGROUND

Increased plasma total homocysteine (tHcy) levels are an independent risk factor for cardiovascular morbidity in patients with normal and impaired renal function, including stable renal transplant recipients (RTRs). Plasma concentrations of the metabolites of Hcy, such as cystathionine (Cys), methylmalonic acid (MMA), 2-methylcitric acid (MC), and its diastereomers MCI and MCII have been reported in only a few articles. We therefore looked for the serum concentration of these metabolites and their relationship to renal function, cardiovascular diseases, the immunosuppressive treatment, and serum concentrations of cobalamin and folate.

METHODS

Fifty RTRs (mean age 50.4 +/- 11.8 years, 35.9 +/- 44.4 months after kidney transplantation) and 35 controls (NP; mean age 43.5 +/- 14.4 years) were studied. Total Hcy and its metabolites were measured by gas chromatography-mass spectrometry (GC-MS).

RESULTS

Total Hcy, MMA, Cys, and MC were elevated twofold to sixfold as compared with NP, with a significant interrelationship between these compounds. With the exception of Cys, they were significantly correlated with serum creatinine. Serum folate levels were inversely correlated with tHcy, Cys and cobalamin with MMA and the ratio of MCI/MCII. There was no correlation between tHcy concentration and its metabolites with immunosuppressive treatment (CsA vs. FK506), clinical history, or current findings of cardiovascular complications and blood pressure profile.

CONCLUSION

Prospective studies are needed to find out whether the lowering or normalization of serum concentrations of tHcy and its metabolites due to treatment with B vitamins should be achieved to reduce the cardiovascular risk and improve the long-term outcome of allografts and of patients.

Ex vivo stimulation of renal tubular p-aminohippurate transport by dexamethasone and triiodothyronine in human renal cell carcinoma

This paper is the third of a long-term planned series of papers dealing with ex vivo investigations of drug transport in human kidney. The aims of this study are (a) to investigate whether or not human renal cell carcinoma (RCC) can actively accumulate p-aminohippurate (PAH) and (b) to test the response of RCC on dexamethasone or triiodothyronine (T3) using tissue slices ex vivo. By this approach, the accumulation capacity of RCC should be stimulated as a prerequisite for an increased uptake of anti-tumour drugs. Tissue slices of RCC samples of 30 patients were incubated for 24 h in Williams medium E containing 0.01-50 microM dexamethasone or T3. Thereafter, slices were placed in PAH-containing Cross-Taggart medium, and PAH uptake into kidney tissue was measured for 2h under standardised conditions as described previously. In intact human renal cortical slices, PAH uptake capacity, expressed as slice to medium ratio (QS/M), was about 2.8 +/- 0.16 after 24 h of incubation and increased significantly in dexamethasone-containing medium in a concentration-dependent manner, up to approximately 150%, whereas T3 did not influence PAH accumulation. On the other hand, in RCC the PAH accumulation capacity was completely abolished (QsM approximately 1). However, after administration of dexamethasone, the accumulated amount of PAH increased significantly in RCC tissue in a concentration-dependent manner, up to approximately 190%. T3 was without effect in RCC, too. Surprisingly, the dexamethasone-mediated stimulation could be differentiated into responders and non-responders, with maximal effects at different concentrations for each patient. Nevertheless, the maximal transport rates remained low in RCC, even under hormone influence. In conclusion, a moderate stimulation of tubular transport capacity can be shown ex vivo in human RCC. This phenomenon is only of a relatively low degree compared with intact renal tissue. However, in principle, the response of RCC on dexamethasone could form a basis for further therapeutic strategies to overcome multi-drug resistance in RCC patients. For this purpose, additional experiments analysing the expression of transporters of the ABC cassette-type are in progress.

[Vertigo drug therapy--merely drug vertigo? Vertigo from the pharmacologic viewpoint]

Vertigo drug therapy is indicated only in few types of vertigo. A causal therapy is possible for infections of the inner ear by antibiotics or antiviral drugs. A symptomatic therapy of severe attacks of vertigo consists in the administration of sedative drugs like antihistaminics, benzodiazepines or neuroleptics. These drugs, however have to be used no longer than one week to avoid an inhibition of beneficial compensatory processes in the central nervous system. Furthermore, the use of non specifically acting blood flow increasing drugs like pentoxifylline in combination with prednisolone can be recommended. For the prophylaxis of Menière's disease, betahistine is the drug of choice because of its two modes of action (beneficial effect on the blood flow in the inner ear, inhibitory effect in vestibular nuclei). For prevention of vomiting as a consequence of vertigo, scopolamine is unsurpassed. In cases of psycogenicly caused vertigo, antivertiginosa from plant origin and homoeopathic drugs can be recommended, especially in the elderly patient, despite the fact that the effect of these drugs can not be fully explained as jet. Beside vertigo drug therapy, vertigo as a side effect of many drugs has to be taken into consideration in clinical routine. The variety of drugs responsible for vertigo consists in relatively harmless substances like aspirin up to substances used in vertigo drug therapy!

The antimicrobial efficacy of a new central venous catheter with long-term broad-spectrum activity

Indwelling vascular catheters are a major cause of nosocomial sepsis. Prevention of colonization of polymeric surfaces by continuous release of bactericidal, highly biocompatible antimicrobials incorporated into polymers has been investigated as a promising new approach. An antimicrobial polyurethane catheter was investigated by HPLC and various antimicrobial assays. Controlled drug delivery governed by the physico-chemical mass transfer from the polyurethane bulk provided long-term release of the antimicrobial substances from the material to the outer surface and catheter lumen. The in vitro activity of catheters coated with miconazole and rifampicin against 158 clinical isolates of catheter-associated infections was evaluated. Incubated in physiological NaCl at 37 degrees C, the half-life of inhibitory activity of catheters coated with miconazole or rifampicin exceeded 3 weeks. In static and dynamic adhesion assays, coated catheters were able to prevent colonization with Staphylococcus aureus, Staphylococcus epidermidis and enterococci. To produce catheters resistant to infection, a potent antimicrobial efficacy combined with an excellent biocompatibility over time is needed. The long lasting efficacy of the antimicrobial polyurethane alloy as well as the increased antifungal activity of miconazole combined with rifampicin may be regarded as a promising improvement for long-term central venous access.

Measurement of ultrasonic-induced chlorhexidine liberation: correlation of the activity of chlorhexidine-silver-sulfadiazine-impregnated catheters to agar roll technique and broth culture

The diagnosis of intravascular catheter-related infections continues to be a challenge to both the clinician and the microbiologist. To assess the antiseptic effects of silver-sulfadiazine-chlorhexidine-impregnated central venous catheters (SSC) on catheter culture systems, segments of fresh antiseptic- and non antiseptic-impregnated catheters as well as extracted catheters following five days of immersion in PBS were sonicated. The chlorhexidine liberated from the catheter material by ultrasonication was measured by HPLC. Fresh antiseptic-impregnated catheter segments rolled on seeded agar plates produced inhibition zones unlike catheters which had been extracted for >five days in phosphate buffered saline (PBS). Scanning electron microscopy (SEM) revealed that chlorhexidine-silversulfadiazine crystals were located in the superficial catheter matrix. Direct contact of superficially located drug particles with seeded agar plates probably caused the inhibition of bacterial growth. The study suggests that antiseptic compounds readily elute from fresh catheters during solid medium-based culturing processes and ultrasonication. The addition of inhibitors of silversulfadiazine-chlorhexidine to media may be prudent especially when culturing antimicrobial loaded catheters removed after short inwelling times.

Determination of the glomerular filtration rate (GFR): methodological problems, age-dependence, consequences of various surgical interventions, and the influence of different drugs and toxic substances

Determinations of renal clearance of fluorescein isothiocyanate (FITC)-inulin were used for assessing the glomerular filtration rate (GFR) in rats and to characterize factors influencing the glomerular filtration capacity. In anesthetized rats, GFR develops after birth up to day 30. Thereafter, GFR remains relatively constant for up to 3 months of age and drops continuously until the 8th month. GFR can be determined in utero, already one day before birth, however, only at a very low level. It increases significantly on the first day of life. Even at this time the effect of furosemide on GFR can be proven. After reduction of renal mass, GFR is decreased in dependence on the extent of kidney tissue removal. However, within 2 days after unilateral nephrectomy (NX) or one week after 5/6 NX, GFR reaches values about 3/4 of the controls with two intact kidneys. Furthermore, the compensation of GFR after renal ischemia reaches 80% of baseline values after one week. On the other hand, GFR is enhanced after bile duct ligation as a model of hepato-renal failure. It has been shown in previous experiments that pretreatment with hormones can stimulate renal tubular transport processes. Pretreatment with dexamethasone or triiodothyronine after 5/6 NX improves glomerular filtration capacity whereas in animals with ligated bile ducts dexamethasone seems to prevent the increase in GFR. After subchronic treatment with epidermal growth factor (EGF) GFR is significantly reduced. A continuous infusion of amino acids does not change GFR in the controls but enhances the filtration capacity in EGF-treated rats. But immediately after bolus injection of amino acids GFR also increases significantly in the controls. Diuretics such as furosemide, most nephrotoxic agents (cyclosporine A [CsA], heavy metals) and imidazole reduce the GFR significantly. Diltiazem reported to act nephroprotectively in CsA nephrotoxicity in human beings was without beneficial effect in rats. This could be due to species differences in GFR because the rat is one of the species with the highest glomerular filtration capacity.

Influence of epidermal growth factor (EGF) on renal transport of PAH and amino acids in amino acid loaded rats

In anaesthetized adult female rats, the influence of epidermal growth factor (EGF) on renal transport of p-amino-hippurate (PAH), electrolytes, and amino acids was investigated. After loading with PAH (200 mg/100 g b.wt. iv.), PAH excretion in EGF treated rats (8 microg/100 g b.wt. subcutaneously for 8 days, twice daily 8 a.m. and 4 p.m.) was increased by about 20 %. Continuous infusions of glutamine, arginine (both 50 mg/100 g b.wt. per hour), or alanine (90 mg/ 100 g b.wt. per hour) were followed by an increase in the fractional excretion (FE) of the administered amino acids as well as of the other endogenous amino acids. Under load conditions (alanine, arginine or glutamine), EGF pretreatment was followed by a stimulation of renal amino acid reabsorption. These changes in amino acid transport were connected with a significant reduction of GFR after EGF pre-treatment (0.96+/-0.10 vs. 0.62+/-0.07 ml/min x 100 g b.wt.), with a distinct increase in sodium excretion (2.98+/-0.55 vs. 4.97+/-0.71 microval/100 g b.wt. x 20 min) and with a retarded normal kidney weight gain (874+/-18 vs. 775+/-32 mg/100 g b.wt.). A simultaneous PAH load reduced amino acid reabsorption as a sign of overloading of renal tubular transport capacity, but in EGF pretreated animals the amino acid excretion was only slightly increased under these conditions.

Renal handling of amino acids in 5/6-nephrectomized rats: stimulation of renal amino acid reabsorption after treatment with triiodothyronine or dexamethasone under amino acid load

In anaesthetized adult female rats, the renal amino acid handling was measured six days after 5/6 nephrectomy (5/6NX). The distinct rise in blood urea nitrogen as well as the significant reduction in urine flow and GFR indicate an impairment of kidney function. In principle, in 5/6NX rats amino acid plasma concentrations were comparable to those of control animals with two intact kidneys, whereas the fractional excretions (FEAA) of most endogenous amino acids measured were significantly enhanced. After bolus injection of leucine or taurine (each 20 mg/100 g b.wt.) or glutamine (90 mg/ 100 g b.wt.), dissolved in 2 ml normal saline per 100 g b.wt., the FEAA of both the amino acids administered and the endogenous amino acids increased as a sign of overloaded amino acid reabsorption capacity. This effect was more pronounced in 5/6NX rats than in controls. As early as one hour after amino acid load, plasma concentrations and FEAA returned to baseline values of 5/6NX rats. A pretreatment with triiodothyronine (20 micrograms/100 g b.wt.) or dexamethasone (60 micrograms/100 g b.wt.), both given intraperitoneally once daily for 3 days, stimulated the renal amino acid transport capacity in 5/6NX rats: the increase in FEAA after amino acid load was significantly lower compared to non-pretreated animals. This stimulation could be shown for the bolus amino acids and the endogenous amino acids and was more distinct in 5/6NX rats than in controls with two intact kidneys.

Epidermal growth factor (EGF) increases the renal amino acid transport capacity in amino acid loaded rats

In anaesthetized adult female rats, the influence of epidermal growth factor (EGF) on renal amino acid handling was investigated in glutamine, arginine (both 50 mg/100 g b.wt. per hour), or alanine (90 mg/100 g b.wt. per hour) loaded animals. Continuous infusions of the three amino acids were followed by an increase in the fractional excretion (FE) of the administered amino acids as well as of the other endogenous amino acids. Under load conditions (alanine, arginine or glutamine), EGF pretreatment (8 micrograms/100 g b.wt. subcutaneously for 8 days, twice daily 8 a.m. and 4 p.m.) was followed by a stimulation of renal amino acid reabsorption. The increase in the fractional excretion of the administered amino acids was significantly lower than in non-EGF-treated rats. These changes in amino acid transport were connected with a significant reduction of GFR after EGF pretreatment (0.96 +/- 0.10 vs. 0.62 +/- 0.07 ml/min x 100 g b.wt.) and a distinct increase in sodium excretion (2.98 +/- 0.55 vs. 4.97 +/- 0.71 muval/100 g b.wt. x 20 min). After loading with p-aminohippurate (PAH; 200 mg/100 g b.wt.), PAH excretion in EGF rats was increased by about 20%, whereas urinary protein excretion was lower in EGF pretreated rats (control: 0.45 +/- 0.04 vs. EGF: 0.18 +/- 0.03 mg/100 g b.wt. x 20 min). The PAH load reduced amino acid reabsorption as a sign of overloading of renal tubular transport capacity, but in EGF pretreated animals the amino acid excretion was only slightly increased under these conditions. Furthermore, EGF pretreatment depressed normal kidney weight gain significantly (874 +/- 18 vs. 775 +/- 32 mg/100 g b.wt.). EGF can improve the renal tubular transport capacity, but, compared to well-known stimulators of renal transport like dexamethasone or triiodothyronine, its effect is only of a moderate degree.

Changes of renal taurine transport after treatment with triiodothyronine or dexamethasone in amino acid loaded rats

In adult female anaesthetized rats, the influence of triiodothyronine or dexamethasone on renal amino acid (AA) handling was investigated in taurine (45 mg/100 g b.wt.) loaded animals. Bolus injections of taurine were followed by temporary increase in fractional excretion (FE(AA)) of taurine as well of the endogenous amino acids which were not administered. Under taurine load conditions, triiodothyronine treatment (20 microg/100 g b.wt. for 3 days, i.p. once daily) was followed by a slight stimulation of the renal taurine reabsorption: the increase in FE(taurine) after taurine load was lower than in untreated rats. Dexamethasone (60 microg/100 g b.wt. for 3 days, i.p. once daily) was without significant effect on FE(taurine) in taurine loaded rats. In non taurine loaded rats there was no hormone influence at all. Similarities and differences between the effects of bolus injections of taurine, glutamine, and leucine on the FE(AA) of these three amino acids were compared in detail to further clarify the reason for the increased amino acid reabsorption capacity after pretreatment with triiodothyronine or dexamethasone.

The hepato-renal syndrome: renal amino acid transport in bile duct ligated rats (DL)--influence of treatment with triiodothyronine or dexamethasone on renal amino acid handling in amino acid loaded rats

The influence of triiodothyronine or dexamethasone on renal amino acid handling was investigated in anaesthetized, bile duct-ligated (DL) adult female rats. 3 days after DL, glomerular filtration rate (GFR) was unchanged whereas urine flow was decreased. Plasma concentrations of 5 out of 16 amino acids were significantly enhanced after DL. On the other hand, the fractional excretion (FE) of 11 out of 16 amino acids was significantly reduced as a sign of improved reabsorption capacity. Bolus injections of leucine (20 mg/100 g b.wt.), glutamine (45 mg/100 g b.wt.), or taurine (45 mg/100 g b.wt.) were followed by a temporary increase in the FE of the administered amino acids as well of the endogenous amino acids which were not administered. This phenomenon was more pronounced in DL than in control rats. Under load conditions, dexamethasone (60 microg/100 g b.wt.) or triiodothyronine (20 microg/100 g b.wt.) treatment for 3 days, i.p. once daily, was followed by a stimulation of renal amino acid reabsorption in DL rats. The increase in fractional amino acid excretion after amino acid load was significantly lower than in untreated rats. This effect was also more pronounced in DL rats.

Is there a beneficial effect of the calcium channel blocker diltiazem on cyclosporine A nephrotoxicity in rats?

To investigate whether or not there is a beneficial effect of diltiazem (D) on cyclosporine A (CsA) nephrotoxicity, renal function, CsA blood levels, and effects of CsA on biotransformation in the liver and on lipid peroxidation were characterized in rats. A single administration of D (60 mg/kg b.wt.) reduced urinary volume (UV), GFR and excretion of Na+ and K+, whereas a single dose of CsA (60 mg/kg b.wt.) alone had no respective effects. P-aminohippurate excretion was almost equal in all groups. Lower doses of D (and CsA) were without effects. After repeated CsA treatment a retardation in body weight gain was seen, with little effect of a co-administration with D hereon. In all tests, thymus mass was reduced by CsA, the weight of spleen, liver, adrenal glands, and kidney were not generally affected by any of the treatments. Furthermore, after repeated administration of CsA and/or D, urinary volume, GFR and Na+ excretion were reduced by CsA, too. Electrolyte concentrations in plasma showed no evident changes by any of the treatments for Na+ and Ca2+. After long time treatment, CsA and CsA + D quite similarly led to higher K+ but lower Mg2+ concentrations in plasma. Only with 7 days highest dosage treatment PAH excretion was reduced significantly by CsA and CsA + D treatment. Surprisingly, CsA levels measured in blood and in kidney tissue, showed lower values after co-administration with D compared to CsA treatment alone. This could be caused by higher activities of monooxygenase functions revealed after pretreatment with D alone. Reduced glutathione (GSH) contents in kidney were elevated in CsA and CsA + D treated groups. In general no significant differences were to be observed concerning lipid peroxidation and stimulated H2O2 formation. Altogether evident protective effects of diltiazem on CsA nephrotoxicity in rats could not be proven.

In vitro stimulation of renal tubular p-aminohippurate transport by dexamethasone in rat kidneys and in intact kidney tissue of patients suffering from renal cell carcinoma

The aim of this study was to test whether or not the accumulation of p-aminohippurate (PAH) can be increased in intact human renal cortical slices obtained from tumor-bearing kidneys of patients suffering from renal cell carcinoma (RCC). Tissue slices were incubated for 24 h in Williams medium E containing 0.01-50 microM dexamethasone. Thereafter slices were placed in PAH-containing Cross-Taggart medium and PAH uptake into kidney tissue was measured for 2 h. In both rat and human renal tissue slices, PAH uptake capacity increased significantly in a concentration-dependent manner after 24 h of incubation in dexamethasone-containing medium (rat, 136%; man, 156%). The stimulatory effect was already significant after 12 h of incubation. In additional experiments it was shown that incubation in triiodothyronine (T3)-containing medium has different effects: in man, T3 does not influence the PAH accumulation capacity of renal cortical slices whereas in rats PAH accumulation is significantly lower after 24 h of incubation with T3. Thus stimulation of tubular transport capacity can be performed in vitro in human renal cortical slices. Discrepancies between the effects of dexamethasone and T3 indicate different modes of action of the two hormones at the cellular level.

In vitro stimulation of renal tubular p-aminohippurate transport by dexamethasone in kidney tissue of immature and adult rats

The in vitro stimulation of the accumulation of p-aminohippurate (PAH) was investigated in renal cortical slices of 10- and 55-day-old rats. For this goal tissue slices were incubated for 24 hours in Williams medium E containing different concentrations of dexamethasone (0.01-5 micromol). After this incubation period slices were placed in PAH containing Cross-Taggart medium and PAH uptake into the kidney tissue was measured for two hours. In both immature and adult rat's tissue slices an active PAH accumulation can be proven after 24 hours incubation without hormone substitution. In both age groups the accumulation capacity after 24 hours incubation reaches about 40-60% of that of acute two hours incubation experiments (slice to medium ratios after two hours of incubation: immature rats: 9.5+/-0.4; adults: 11.4+/-0.3). In the acute incubation experiments there was no influence of dexamethasone on PAH accumulation whereas after 24 hours incubation dexamethasone significantly increases the PAH uptake capacity in a concentration dependent manner: 10- and 55-day-old rats: 26 and 36 (65) % increase, respectively. It can be concluded that 1.) a stimulation of tubular transport capacity can be performed in vitro, and 2.) discrepancies between in vitro and in vivo stimulation exist concerning PAH accumulation in renal cortical slices.

Influence of vitamin E treatment on glutathione system after renal ischemia in immature and adult rats

Survival rates were not significantly different 5 days after 20-min unilateral ischemia followed by contralateral nephrectomy: 58% in 20-day-old vs. 77% in 55-day-old rats. This experimental approach was used to characterize age dependent differences in the susceptibility of the glutathione system to ischemia and protective effects of treatment with vitamin E (10 mg/100 g b.wt. once daily s.c.) on the outcome after renal ischemia. The degree of postischemic changes (GSH, gamma-GT, TBARS) was the highest on days 1 and 2 after ischemia; at this time, survival rates were similar in young and adult rats. In adult animals, both glutathione content and the activity of gamma-GT were significantly reduced after ischemia whereas in immature rats only the glutathione content was distinctly diminished. At the 5th day after ischemia the parameters were almost normalized in the two age groups. Repeated administration of vitamin E improved the survival rate in adult rats up to 100%; in young animals, lethality was not influenced by vitamin E treatment. This reflects the beneficial effects of vitamin E on the glutathione system in adults whereas the vitamin was without effect on the immature rats' glutathione system.

Kidney function in rats after 5/6 nephrectomy (5/6 NX); effort of treatment with vitamin E

In adult female rats various kidney functions were measured 3 weeks after 5/6 nephrectomy (5/6 NX). The distinct rises in blood urea nitrogen and in renal excretion of proteins indicate the impairment of the kidney. In 5/6 NX rats, the renal excretion of creatinine, glucosaminoglycan, and of p-aminohippurate was diminished. The concentrations of hydroxypyroline and of free hydrogen ions were distinctly increased in urine samples from 5/6 NX rats. The concentration of lipid peroxides was enhanced in kidney tissue whereas 3 weeks after 5/6 NX the concentration of GSH and GSSG in the remnant kidney tissue was unchanged. Long-term administration of vitamin E increased its concentration in plasma, kidney, and liver. Nevertheless, daily treatment with vitamin E (1 or 10 mg/100 g b.w. s.c. for 5 weeks) did not reduce the degree of impairment of kidney function following 5/6 NX.

Protective effects of methimazole against cisplatin-induced nephrotoxicity in rats

In adult rats 6 mg kg-1 body wt. cisplatin given i.p. was nephrotoxic. Four days of i.p. treatment with 40 mg kg-1 body wt. methimazole, which started 1 day before CP, prevented increases in blood urea nitrogen and in the renal excretion of proteins. Furthermore, methimazole treatment reduced the oliguric effect of cisplatin and the depression of renal sodium excretion. However, it had no effect on the increased formation of lipid peroxides in cisplatin-damaged kidneys, although repeated treatment with methimazole enhanced the renal glutathione content. Methimazole acts as a radical scavenger, maintaining the glutathione pool in the kidney.