Mechanism of Cd-Induced Inhibition of Na-Glucose Cotransporter in Rabbit Proximal Tubule Cells: Roles of Luminal pH and Membrane-Bound Carbonic Anhydrase

Background/Aims: We have previously reported that a complex of cadmium-metallothionein (Cd-MT) directly affects the apical Na-glucose cotransporter on the luminal side in proximal tubules, suggesting that Cd-MT is more toxic than CdCl2 in causing tubulopathy. To find the potential mechanisms, we evaluated the effect of luminal pH alteration and carbonic anhydrase (CA) inhibition on Cd-MT-induced reduction of glucose-dependent transmural voltage in rabbit S2 segments perfused in vitro. Methods: Before and after the addition of Cd-MT (1 µg Cd/ml) to the lumen, the deflections of transmural voltage upon the elimination of glucose from the perfusate (DeltaVtglu) were measured as a parameter of activity of the Na-glucose cotransporter. Results: During perfusion with a control solution of pH 7.4, the DeltaVtglu significantly decreased after addition of Cd-MT for 10 min. A reduction in pH to 6.8 significantly shortened the time needed to reduce the DeltaVtglu to 20 min. Furthermore, simultaneous addition of acetazolamide with control perfusate prevented the reduction. P-Fluorobenzyl-aminobenzolamide (pFB-ABZ), a membrane-impermeable CA inhibitor, added to the lumen also completely prevented the reduction in DeltaVtglu. In rabbits with chronic Cd exposure, acetazolamide prevented the glucosuria. Conclusion: Cd-MT-induced inhibition of Na-glucose cotransporter activity in the S2 segment strongly depends on luminal pH, and that an increase in pH by inhibition of luminal membrane-bound CA is useful to prevent renal Cd toxicity

Einfluß von Chrom, Kupfer und Zinn auf die Aktivität des Kohlenstoffs in flüssigem Stahl mit höherem Kohlenstoffgehalt

Um die Kohlenstoffaktivität in Fe-C Lösungen und den Wirkungsparameter ε(X)/C=(∂ 1nγc/∂Nₓ)Nc (X ist das Zusatzelement Chrom, Kupfer und Zinn) bei Kohlenstoff-gehalten zwischen 0.4〜1.4 Gew. %C zu bestimmen, wurde die Konzentration des Kohlenstoffs oder der Zusatzelemente in flüssigen Fe-C und Fe-C-X Systemen unter der Atmosphäre eines Gasgemisches aus Kohlenoxyd und Kohlendioxyd bei 1550°C gemessen. Aus der vorliegenden Untersuchung ergaben sich die Abhängigkeit des Kohlenstoff-aktivitätskoeffizienten von der Kohlenstoffkonzentration und die Wirkungsparameter ε(X)/C=(∂ 1nγc/∂Nₓ)Nc

Basolateral Na+/H+ exchange maintains potassium secretion during diminished sodium transport in the rabbit cortical collecting duct

Stimulation of the basolateral Na+/K+-ATPase in the isolated perfused rabbit cortical collecting duct by raising either bath potassium or lumen sodium increases potassium secretion, sodium absorption and their apical conductances. Here we determined the effect of stimulating Na+/K+-ATPase on potassium secretion without luminal sodium transport. Acutely raising bath potassium concentrations from 2.5 to 8.5 mM, without luminal sodium, depolarized the basolateral membrane and transepithelial voltages while increasing the transepithelial, basolateral and apical membrane conductances of principal cells. Fractional apical membrane resistance and cell pH were elevated. Net potassium secretion was maintained albeit diminished and was still enhanced by raising bath potassium, but was reduced by basolateral ethylisopropylamiloride, an inhibitor of Na+/H+ exchange. Luminal iberitoxin, a specific inhibitor of the calcium-activated big-conductance potassium (BK) channel, impaired potassium secretion both in the presence and absence of luminal sodium. In contrast, iberitoxin did not affect luminal sodium transport. We conclude that basolateral Na+/H+ exchange in the cortical collecting duct plays an important role in maintaining potassium secretion during compromised sodium supplies and that BK channels contribute to potassium secretion

Simultaneous Diffusion Coating of Cr and Si on Stainless Steel using Fluoride-Free Activator

The simultaneous deposition of chromium and silicon on stainless steel using a halide-activated diffusion coating process was performed to improve oxidation properties at high temperatures. Conventional procedure in diffusion coating process uses an activator containing fluoride. Fluoride is harmful for the human body and the environment. This experimental object is a development of the fluoride-free activator in diffusion coating of chromizing-siliconizing. In this investigation, Cr-Si intermetallic compound layers were coated on stainless steel by the pack cementation to improve its oxidation resistance and the resulting properties of the obtained coatings were investigated. The pack powders used for the diffusion coating were Cr and Si as diffusion element, Al2O3 as filler, and NH4Cl and CaCl2 as fluoride-free activator or NH4Cl, NaF and AlF3 as fluoride-added activator. The diffusion coating treatment was conducted at 1323 K for 18.0 ks in an Ar atmosphere. After the simultaneous deposition of chromium and silicon on stainless steel, a modified layer was observed on the treated sample surface and fluoride-free activator could also modify the steel surface using pack cementation

Evaluation of the interaction between nonsteroidal anti-inflammatory drugs and methotrexate using human organic anion transporter 3-transfected cells

Coadministration of methotrexate and nonsteroidal anti-inflammatory drugs (NSAIDs) can cause a pharmacokinetic interaction and a subsequent increase in blood methotrexate concentrations. methotrexate and most NSAIDs are excreted into urine via organic anion transporter 3 (OAT3). The purpose of this study was to evaluate NSAIDs that compete less with methotrexate by using the renal cell line stably expressing human OAT3 (S2-hOAT3) in vitro. We also confirmed the pharmacokinetic interaction of methotrexate with NSAIDs in vivo. [3H]methotrexate uptake into S2-hOAT3 cells was inhibited by most NSAIDs in a concentration-dependent manner, but aspirin, salicylate, tiaramide, and acetaminophen did not inhibit uptake. Inhibition by sulindac and pranoprofen was weaker at therapeutic drug concentrations. Furthermore, methotrexate concentrations in rat serum were significantly increased in a NSAID concentration-dependent manner when concentrations of coadministered NSAIDs increased above the Ki values obtained in the in vitro study. On the other hand, drugs that were not substrates of hOAT3, such as acetaminophen, did not interact with methotrexate. The magnitude of the pharmacokinetic interaction between methotrexate and NSAIDs was significantly correlated with results of the accumulation study in vitro and was not significantly correlated with a reduction of urinary creatinine excretion. In conclusion, methotrexate and most NSAIDs are substrates of hOAT3, and those drugs compete via hOAT3 in tubular secretion, the major mechanism of the interaction between methotrexate and NSAIDs. The accumulation study using S2-hOAT3 cells might be useful for screening of potential interactions between methotrexate and new NSAIDs in vivo

Profile of rhythmic gene expression in the livers of obese diabetic KK-Ay mice

金沢大学大学院医学系研究科環境社会医学Although a number of genes expressed in most tissues, including the liver, exhibit circadian regulation, gene expression profiles are usually examined only at one scheduled time each day. In this study, we investigated the effects of obese diabetes on the hepatic mRNA levels of various genes at 6-h intervals over a single 24-h period. Microarray analysis revealed that many genes are expressed rhythmically, not only in control KK mice but also in obese diabetic KK-Ay mice. Real-time quantitative PCR verified that 19 of 23 putative circadianly expressed genes showed significant 24-h rhythmicity in both strains. However, obese diabetes attenuated these expression rhythms in 10 of 19 genes. More importantly, the effects of obese diabetes were observed throughout the day in only two genes. These results suggest that observation time influences the results of gene expression analyses of genes expressed circadianly. © 2006 Elsevier Inc. All rights reserved

Prostaglandin E2 receptor type 2-selective agonist prevents the degeneration of articular cartilage in rabbit knees with traumatic instability

[Introduction]Osteoarthritis (OA) is a common cause of disability in older adults. We have previously reported that an agonist for subtypes EP2 of the prostaglandin E2 receptor (an EP2 agonist) promotes the regeneration of chondral and osteochondral defects. The purpose of the current study is to analyze the effect of this agonist on articular cartilage in a model of traumatic degeneration. [Methods]The model of traumatic degeneration was established through transection of the anterior cruciate ligament and partial resection of the medial meniscus of the rabbits. Rabbits were divided into 5 groups; G-S (sham operation), G-C (no further treatment), G-0, G-80, and G-400 (single intra-articular administration of gelatin hydrogel containing 0, 80, and 400 μg of the specific EP2 agonist, ONO-8815Ly, respectively). Degeneration of the articular cartilage was evaluated at 2 or 12 weeks after the operation. [Results]ONO-8815Ly prevented cartilage degeneration at 2 weeks, which was associated with the inhibition of matrix metalloproteinase-13 (MMP-13) expression. The effect of ONO-8815Ly failed to last, and no effects were observed at 12 weeks after the operation. [Conclusions]Stimulation of prostaglandin E2 (PGE2) via EP2 prevents degeneration of the articular cartilage during the early stages. With a system to deliver it long term, the EP2 agonist could be a new therapeutic tool for OA

Pharmacokinetics and pharmacodynamics of insulin aspart in patients with Type 2 diabetes: Assessment using a meal tolerance test under clinical conditions

Few studies have evaluated the pharmacokinetics of rapid-acting insulin analogues in patients with Type 2 diabetes, especially under clinical conditions. The aim of the present study was to assess both the pharmacokinetics and pharmacodynamics of insulin aspart in Type 2 diabetic patients who were being treated with the analogue alone. Meal tolerance tests with and without self-injection of a customary dose of insulin aspart (0.05-0.22 U/kg) were conducted in 20 patients in a randomized cross-over study. The dose of insulin aspart (per bodyweight) was significantly correlated with both the maximum concentration (r 2 = 0.59; P < 0.01) and area under the concentration-time curve for insulin aspart (r 2 = 0.53; P < 0.01). However, the time to maximum concentration (T max), which varied widely from < 60 to ≥ 120 min, was not associated with either dosage (r 2 = 0.02; P = 0.51) or body mass index (r 2 = 0.02; P = 0.57). Injection of insulin aspart exacerbated delayed hyperinsulinaemia after meal loading, mainly in patients with T max ≥ 120 min. With regard to pharmacodynamics, insulin aspart had favourable effects on postprandial hyperglycaemia, hyperglucagonaemia and hyperlipidaemia. The T max for this insulin analogue differed greatly between individuals and delayed hyperinsulinaemia was particularly exacerbated in patients with higher T max values. Identification of the factors contributing to interindividual variation in the absorption lag time is essential for improving the efficacy and safety of insulin aspart. © 2012 The Authors. Clinical and Experimental Pharmacology and Physiology © 2012 Blackwell Publishing Asia Pty Ltd

The hepatic circadian clock is preserved in a lipid-induced mouse model of non-alcoholic steatohepatitis

金沢大学医薬保健研究域医学系Recent studies have correlated metabolic diseases, such as metabolic syndrome and non-alcoholic fatty liver disease, with the circadian clock. However, whether such metabolic changes per se affect the circadian clock remains controversial. To address this, we investigated the daily mRNA expression profiles of clock genes in the liver of a dietary mouse model of non-alcoholic steatohepatitis (NASH) using a custom-made, high-precision DNA chip. C57BL/6J mice fed an atherogenic diet for 5 weeks developed hypercholesterolemia, oxidative stress, and NASH. DNA chip analyses revealed that the atherogenic diet had a great influence on the mRNA expression of a wide range of genes linked to mitochondrial energy production, redox regulation, and carbohydrate and lipid metabolism. However, the rhythmic mRNA expression of the clock genes in the liver remained intact. Most of the circadianly expressed genes also showed 24-h rhythmicity. These findings suggest that the biological clock is protected against such a metabolic derangement as NASH. © 2009 Elsevier Inc. All rights reserved