Competitive Inhibition of p-Aminohippurate Transport by Quinapril in Rabbit Renal Basolateral Membrane Vesicles

The mechanism of quinapril's interaction with the organic anion transporter was characterized by studying its effect on the transport of p-aminohippurate (PAH) in rabbit renal basolateral membrane vesicles (BLMV). Cis-inhibition studies demonstrated that quinapril was a specific and potent inhibitor of PAH. The K_i of quinapril was about 20 M, a value similar to that of probenecid and eight-times lower than the K_m value of 165 M for PAH. Even though quinapril resulted in trans-inhibition of PAH uptake during counterflow studies, kinetic studies revealed that quinapril was a competitive inhibitor of PAH transport. This latter finding suggests that quinapril and PAH share a common binding site on the transporter. Overall, the results indicate that quinapril is a high-affinity inhibitor of the organic anion transporter in renal BLMV, and that drug–drug interactions may occur with other organic anions at the basolateral membrane of proximal cells.     

Characterization of Guanidine Transport in Human Renal Brush Border Membranes

Purpose. Organic cation transporters in the renal proximal tubule are important in the secretion of many clinically used drugs and their metabolites. The goal of this study was to determine the mechanisms of guanidine transport in human kidney. Methods. Brush-border membrane vesicles were prepared from donor human kidneys deemed unsuitable for renal transplantation. Results. Uptake of [¹⁴C]-guanidine (50 M) in the vesicles, as determined by rapid filtration, was significantly greater in the presence of an outwardly-directed proton gradient, at all early time points, than in the absence of the gradient. Proton-stimulated uptake of [¹⁴C]-guanidine at 30 sec (32.0 ± 1.24 pmol/mg protein) was significantly inhibited by a number of organic cations including 5 mM unlabeled guanidine (14.8 ± 1.84 pmol/mg protein) and 5 mM MIBA (9.14 ± 3.80 pmol/ mg protein), but not by 5 mM TEA (28.4 ± 5.67 pmol/mg protein). Guanidine, but not TEA, trans-stimulated [¹⁴C]-guanidine uptake. Conversely, TEA, but not guanidine, trans-stimulated [¹⁴C]-TEA uptake in the vesicles. The proton-dependent transport of guanidine was characterized by a K_m of 3.52 ± 0.42 mM (SE) and a V_max of 34.6 ± 8.64 pmol/mg protein/sec (SE). Conclusions. These results demonstrate that guanidine transport in human renal brush border membrane vesicles is stimulated by a proton gradient. Evidence was obtained suggesting that the transporter for guanidine is distinct from the previously described organic cation proton antiporter for TEA.     

Decreased Lithium Disposition to Cerebrospinal Fluid in Rats with Glycerol-induced Acute Renal Failure

PURPOSE: The lithium disposition to cerebrospinal fluid (CSF) was evaluated in rats with acute renal failure (ARF) to examine whether electrolyte homeostasis of the CSF is perturbed by kidney dysfunction. In addition, the effects of renal failure on choroid plexial expressions of the Na(+)-K(+)-2Cl(-) co-transporter (NKCC1) and Na(+)/H(+) exchanger (NHE1) were also studied. METHODS: After lithium was intravenously administered at a dose of 4 mmol/kg, its concentration profile in plasma was evaluated by collecting plasma specimens, while that in CSF was monitored with a microdialysis probe in the lateral ventricles. NKCC1 and NHE1 expressions were measured via the Western immunoblot method using membrane specimens prepared from the choroid plexus in normal and ARF rats. RESULTS: The lithium concentration in CSF of ARF rats was 30% lower than that of normal rats, while their plasma lithium profiles were almost the same, indicating that the lithium disposition to CSF was decreased in ARF rats. It was revealed that the choroid plexial expression of NKCC1 was increased by 40% in ARF rats, but that of NHE1 was unchanged. CONCLUSION: ARF decreases the lithium disposition to CSF, possibly by promoting lithium efflux from CSF due to increased NKCC1 expression in the choroid plexus.     

Transport of Levofloxacin in the OK Kidney Epithelial Cell Line: Interaction with p-Aminohippurate Transport

Purpose. To evaluate the mechanism of renal transport of quinolone antibacterial drugs, we examined the interaction of levofloxacin with p–aminohippurate (PAH) transport systems and the transport of levofloxacin in renal epithelial cells. Methods. Transport of [¹⁴C]PAH or [¹⁴C]levofloxacin was measured using OK cell monolayers grown on microporous membrane filters. Results. Transcellular transport from the basolateral to the apical side and cellular accumulation of [¹⁴C]PAH were inhibited by levofloxacin. Both the initial uptake of [¹⁴C]PAH from the basolateral side and the efflux to the apical side were inhibited by levofloxacin. The basolateral–to–apical transcellular transport of [¹⁴C]levofloxacin was greater than that in the opposite direction. [¹⁴C]Levofloxacin efflux to the apical side was greater than that to the basolateral side. Unlabeled levofloxacin and grepafloxacin inhibited the transcellular transport of [¹⁴C]levofloxacin, accompanied by an increase of cellular accumulation. However, neither PAH nor an anion transport inhibitor 4–4–diisothiocyanostilbene–2,2–disulfonic acid (DIDS) affected the basolateral–to–apical transport of [¹⁴C]levofloxacin nor its uptake from the basolateral side. Conclusions. These results indicated that levofloxacin inhibits PAH transport across both the basolateral and apical membranes of OK cells, but are not transported via the systems for PAH transport. The existence of a specific transport system for quinolones was indicated in OK cells.     

Effect of Acute Renal Failure on Neurotoxicity of Cimetidine in Rats

Purpose. We investigated the effect of acute renal failure on the neurotoxicity of cimetidine in rats. Methods. Experimental acute renal failure was produced by bilateral ureteral ligation. Cimetidine was intravenously infused to ureter ligated (UL) and control rats, and cimetidine concentration in plasma, brain and cerebrospinal fluid (CSF) were compared. Results. The cimetidine concentration in plasma was rapidly increased in UL rats as compared to control rats. The cimetidine concentration in CSF at the onset of convulsion did not depend on the infusion rate, suggesting that cimetidine in CSF equilibrates rapidly with the site of action for clonic convulsion. The cimetidine concentration in CSF of UL rats at the onset of clonic convulsion was lower than those of control rats. Conclusions. Increased sensitivity to the drug on the central nervous system may contribute to increased toxicity of cimetidine with renal failure.     

Effect of Cisplatin-Induced Acute Renal Failure on Bioavailability and Intestinal Secretion of Quinolone Antibacterial Drugs in Rats

PURPOSE: The aim of this study was to clarify the effects of renal failure on intestinal secretion of quinolone antibacterial drugs. METHODS: Pharmacokinetics of grepafloxacin, levofloxacin, and ciprofloxacin in cisplatin-induced acute renal failure (ARF) rats were evaluated, and intestinal and biliary clearance studies were examined. Transport experiments using culture cells were performed. RESULTS: The bioavailability of grepafloxacin in ARF rats was 1.2-fold higher than that in normal rats. On the other hand, the bioavailability of ciprofloxacin in ARF rats was markedly decreased to half of that in normal rats, and that of levofloxacin was not changed. Intestinal clearance of grepafloxacin in ARF rats was 75% of that in normal rats, whereas that of ciprofloxacin was 1.4-fold higher than in normal rats, and that of levofloxacin was comparable between normal and ARF rats. Transport experiments using P-glycoprotein-expressing LLC-GA5-COL150 cells and human intestinal Caco-2 cells suggested that grepafloxacin and levofloxacin were substrates of P-glycoprotein and that ciprofloxacin was not, and that intestinal secretion of ciprofloxacin was mediated by a specific transport system distinct from organic cation and anion transporters and multidrug resistance-associated protein 2. CONCLUSIONS: Cisplatin-induced ARF differentially modulated the bioavailability and intestinal secretion of quinolones in rats.     

Involvement of Indoxyl Sulfate in Renal and Central Nervous System Toxicities During Cisplatin-induced Acute Renal Failure

Purpose The purpose of the present study was to explore the involvement of indoxyl sulfate (IS) in nephrotoxicity and central nervous system (CNS) toxicity in cisplatin (CDDP)-treated rats. Materials and Methods Renal function was evaluated by serum creatinine and BUN levels. The IS levels in the serum, brain and kidney was monitored by high-performance liquid chromatography method. Body weight and rectal temperature were monitored. Real-time PCR analysis was performed to examine rPer2 mRNA expression. Results Renal function deteriorated in a time-dependent manner after administration of CDDP. The concentration of IS in the serum, brain and kidney markedly increased 24–84 h after commencement of CDDP treatment. The observed increase in the levels of serum creatinine, BUN and IS was suppressed by concomitant administration of AST-120. Rectal temperature was significantly lowered 72–92 h after CDDP-treatment, which was partially restored by coadministration of AST-120. Moreover, the amplitude of rectal temperature rhythms was disrupted by treatment with CDDP. Circadian rhythm of rPer2 mRNA expression, a clock gene, in suprachiasmatic nucleus (SCN) and kidney was disturbed in CDDP-treated rats. Conclusions An increase in the IS level and the associated disturbance to the circadian rhythm are involved in the renal and CNS toxicities in CDDP-treatment. K.I. and H.W. contributed equally to this work.     

204例急性肾功能衰竭临床分析

目的：总结分析204例急性肾功能衰竭病因及其临床表现。方法：分析我院204例急性肾功能衰竭的病因分布及临床表现。结果：204例急性肾功能衰竭中有143例为中毒性,占70.09%。其中生物性中毒101例,占中毒性急性肾功能衰竭的70.63%;药物性29例,占20.28%。结论：急性肾功能急竭中,中毒性占较大比例,而又以生物毒常见,药物性次之。及时透析是成功救治病人的关键措施。     

Decreased Systemic Clearance of Diltiazem with Increased Hepatic Metabolism in Rats with Uranyl Nitrate-Induced Acute Renal Failure

The effect of uranyl nitrate (UN)-induced acute renal failure (ARF) on the pharmacokinetics of diltiazem (DTZ) was examined in rats through in vitro and in vivo studies. In vitro homogenate studies demonstrated that DTZ was metabolized to deacetyl diltiazem (DAD) predominantly in the liver. Metabolism in the small intestine, kidney, or blood pool was negligible compared with that in the liver. UN-induced ARF (UN-ARF) increased the in vitro hepatic clearance (CLvit) of DTZ 1.4-fold. In vivo pharmacokinetic studies following intravenous (iv) and portal venous (pv) administration revealed that UN-ARF increased the intrinsic clearance (CLi) of DTZ from 243.0 to 414.5 ml/min/kg but decreased its total plasma clearance (CLt) from 90.3 to 64.3 ml/min/kg. The increase in CLi was consistent with the increase in CLvit of the liver. The in vitro plasma free fraction of DTZ (fp) was decreased from 0.25 to 0.14 by UN-ARF, but the in vitro blood/plasma partition of DTZ (Rb) remained constant at unity. From the CLi and fp changes, the plasma intrinsic clearance for unbound DTZ (CLi) was calculated to be increased 2.7-fold, from 1104.5 to 2960.7 ml/min/kg, by UN-ARF. The fp decrease was also reflected in the steady-state distribution volume (Vdss) of DTZ, which was decreased significantly from 3595.5 to 2528.3 ml/kg. The absolute bioavailability of pv DTZ (Fpv) was decreased by UN-ARF from 37.5 to 15.5% but was still much higher than the reported oral bioavailability (6%), indicating poor absorption of DTZ from the GI tract. From the calculation based on a well-stirred pharmacokinetic model, DTZ was found to increase the hepatic blood flow (HBF) of the control rats more than twofold at doses of 3 mg/kg (iv) or 10 mg/kg (pv), possibly due to the vasodilating effect of DTZ. However, the effect of DTZ on HBF was not present in the UN-ARF rats. It is not clear at present whether this could be attributed to vasoconstricting effects of UN-ARF or blockade of the vasodilating effect of DTZ.     

Renal Tubular Handling of p-Aminohippurate and Epidermal Growth Factor (EGF) in Filtering and Nonfiltering Perfused Rat Kidneys

We examined the integrity of renal tubular function in filtering and nonfiltering isolated perfused rat kidneys by using p-amino-³H-hippurate (³H-PAH) and the multiple indicator dilution method with ¹⁴C-creatinine as a reference. The influx clearance (PS_U,l) of unbound ³H-PAH was 0.37 and 0.38 ml/sec in the filtering and nonfiltering kidneys, respectively. The efflux rate constants were comparable between filtering and nonfiltering kidneys, while the sequestration rate constant in the filtering kidney was approximately three times larger than that in the nonfiltering kidney. These data suggest that the nonfiltering kidney maintains ³H-PAH transporting ability through the antiluminal plasma membrane. The renal handling of epidermal growth factor (EGF) by filtering and nonfiltering kidneys was compared. The ratio of the total uptake of tracer ¹²⁵I-EGF over 20 min in the nonfiltering kidney to that in the filtering kidney was 0.8. This ratio was reduced to 0.2 when the kidneys were perfused with tracer ¹²⁵I-EGF plus 20 nM EGF. Furthermore, the total uptake of tracer ¹²⁵I-EGF in the nonfiltering kidney was reduced 20-fold in the presence of 20 nM unlabeled EGF. These findings suggest that the tubular uptake of tracer ¹²⁵I-EGF by filtering kidney takes place mainly via the antiluminal plasma membrane and that this uptake is a saturable process.     

Effect of Substituted Benzoylglycines (Hippurates) and Phenylacetylglycines on p-Aminohippurate Transport in Dog Renal Membrane Vesicles

The effect of substituted benzoylglycines (hippurates) and phenylacetylglytines on the transport of p-aminohippurate (PAH) was studied in basolateral (BLMV) and brush border membrane vesicles (BBMV) isolated from dog kidney cortex. The probenecid-sensitive part of 100 µM [³H]PAH uptake into BLMV and BBMV was measured in the presence and absence of 5 mM glycine conjugate. The benzoyl- and phenylacetylglycines studied were substituted in the 2-, 3-, or 4-position with an H, CH₃, OCH₃ or OH group. Benzoylglycines were stronger inhibitors of PAH transport than phenylacetylglycines and the inhibitory potency of the conjugates was in general lower against the transporter in BBMV than BLMV. The specificities of the transporters in both membranes appear to be very similar. The inhibitory potency of the benzoylglycines, expressed as the apparent inhibition constant (logK _i), did not show a linear relationship with their lipophilicity as determined by reversed phase HPLC. Deviation from linearity was caused mainly by the 3-OH and 4-OH analogs, which showed a greater inhibitory potency than expected from their lipophilicity. Phenylacetylglycines only showed a small variation in logK _i, values, indicating that insertion of a CH₂ group between the ring and the carbonyl practically abolishes the influence of the ring and its substituents. In conclusion, both hydrophobic and electronic properties are important determinants of affinity for the PAH transport system. An additional partially negative hydroxyl group in the ring, located preferably at the 3- or 4-position, increases the interaction with the transport system.     

Modulation of Organic Cation Transport and Lipid Fluidity by Benzyl Alcohol in Rat Renal Brush-border Membranes

Purpose. Organic cations are actively transported in renal brush-border membranes (BBM) by the H⁺/organic cation antiport system. In the present study, we investigated the relationship between membrane fluidity and organic cation transport in the BBM. Methods. The effects of benzyl alcohol, a membrane fluidizing agent, on the organic cation tetraethylammonium (TEA) uptake were studied using renal BBM vesicles isolated from rat kidney. BBM fluidity was assessed by fluorescence polarization technique. Results. H⁺ gradient-dependent uptake of TEA in BBM vesicles was inhibited by benzyl alcohol in a dose-dependent manner, with an apparent half inhibitory concentration of 18mM. The decrease in fluorescence anisotropy of l,6-diphenyl-l,3,5-hexatriene in BBM, which represents the increase in membrane fluidity, was correlated with the decrease in TEA transport activity. The dissipation rate of H⁺ gradient, a driving force for organic cation transport in BBM, was increased by benzyl alcohol. In addition, H⁺ gradient-independent TEA-TEA exchange was also inhibited by benzyl alcohol. These findings indicate that benzyl alcohol inhibits the uptake of TEA by affecting the intrinsic activity of the organic cation transporter and the H⁺ gradient dissipation rate. Conclusions. The membrane fluidity should be an important determinant for organic cation transport in renal BBM.     

Restored expression and activity of organic ion transporters rOAT1, rOAT3 and rOCT2 after hyperuricemia in the rat kidney

We previously reported that in hyperuricemic rats, renal impairment occurred and organic ion transport activity decreased, accompanied with a specific decrease in the expression of rat organic anion transporters, rOAT1 and rOAT3, and organic cation transporter, rOCT2. In the present study, we investigated the reversibility of the organic ion transport activity and expression of organic ion transporters (slc22a) during recovery from hyperuricemia. Hyperuricemia was induced by the administration of a chow containing uric acid and oxonic acid, an inhibitor of uric acid metabolism. Four days after discontinuance of the chow, the plasma uric acid concentration returned to the normal level, and renal functions such as creatinine clearance and BUN levels were restored, although the recovery of tubulointerstitial injury was varied in sites of the kidney. Basolateral uptake of p-aminohippurate (PAH) and tetraethylammonium (TEA), and both protein and mRNA levels of rOAT1, rOAT3 and rOCT2 in the kidney gradually improved during 14 days of recovery from hyperuricemia. Basolateral PAH transport showed a higher correlation with the protein level of rOAT1 (r(2)=0.80) than rOAT3 (r(2)=0.34), whereas basolateral TEA transport showed a strong correlation with rOCT2 protein (r(2)=0.91). The plasma testosterone concentration, which is a dominant factor in the regulation of rOCT2, was gradually restored during the recovery from hyperuricemia, but the correlation between the plasma testosterone level and rOCT2 protein expression in the kidney was not significant. These results suggest that the regulation of organic ion transporters, rOAT1, rOAT3 and rOCT2, by hyperuricemia is reversible, and the organic ion transport activity restores according to the expression levels of these transporters.     

Urinary Excretion and Diuretic Action of Furosemide in Rats: Increased Response to the Urinary Excretion Rate of Furosemide in Rats with Acute Renal Failure

A urinary excretion–response curve representing the urinary excretion rate of furosemide versus the urinary excretion rate of (Na⁺ + K⁺) was used to analyze furosemide action in rats with uranyl nitrate-induced acute renal failure (ARF) with and without dopamine coadministration. Urinary excretion of furosemide, but not its serum concentration, was the determinant for the diuretic action of furosemide. Increased diuretic response was observed in ARF rats, although the total diuretic response and urinary recovery of furosemide within 2 hr decreased. Dopamine enhanced furosemide-induced diuresis in ARF rats in terms of the total urine output and urinary electrolyte excretion, although the urinary excretion–response curves were not different. This enhancement by dopamine was found to be caused by the augmented urinary excretion of furosemide and the increased response to this drug in ARF rats. These findings suggest the contribution of decreased concentrating ability along the nephron and/or increased sensitivity of cells at the site of action to this drug.     

Moment analysis of drug disposition in kidney. VI: Assessment ofin vivo transmembrane transport ofp-aminohippurate in tubular epithelium

This paper describes a novel method to assess the antiluminal membrane (ALM) and luminal membrane (LM) transport in vivo across renal tubular epithelial cells. The method is based upon a noncompartmental moment analysis of the plasma concentration and urinary excretion rate curves following renal artery injection. Quantitative relationships are represented between the noncompartmental parameters (clearance, volume of distribution, and the mean transit time) and the first-order rate constants associated with transmembrane transport processes. The in vivo transepithelial transport of [¹⁴C]p -aminohippurate (PAH) was examined using the rat kidney in the absence or presence of various plasma concentrations of unlabeled PAH, cefazolin, and methotrexate. The tubular secretion intrinsic clearance was reduced with an increase in the plasma concentration of concurrent unlabeled organic onions. The distribution volume of PAH in the kidney decreased in association with a decrease in the amount of PAH secreted, whereas the mean transepithelial (artery-to-lumen) transit time (¯T_cell) remained constant. These findings indicate that ALM transport is a capacity-limited process determining the amount of tubular secretion, and that LM transport is linear over the concentration range examined and independent of the amount of secretion. The contribution of ALM and LM transport to transcellular transport was first clarified in vivo. The present method will be useful for analyzing the transmembrane transport processes in vivo for highly diffusible substances in the kidney.     

阿昔洛韦致急性肾功能衰竭及不合理用药分析

通过研究国内外文献资料及我国和世界卫生组织不良反应数据库数据,分析阿昔洛韦致急性肾功能衰竭的发生情况、临床特征、发病机制和不合理用药现状,强调合理用药、开展药物警戒工作的重要性。     

纳洛酮对大鼠肾脏缺血再灌注损伤的保护作用

利用大鼠肾脏缺血再灌注损伤模型,观察了纳洛酮(NAL)对肾缺血再灌注后血中丙二醛(MDA)、超氧化物歧化酶(SOD)及肾组织中Na~ ,K~ —ATP酶和Ca~( )—ATP酶的影响,并观察组织病理学变化。结果显示缺血再灌注后血MDA含量明显升高,SOD活力明显降低,肾组织Na~ ,K~ —ATP酶和Ca~( )—ATP酶活力均显著降低。用NAL(2mg/kg与4mg/kg,ip)后MDA显著下降,SOD和Na~ ,K~ —ATP酶和Ca~( )—ATP酶活力均明显升高。组织病理学检查显示,应用NAL后肾小管上皮细胞的损伤明显减轻。结果提示NAL对肾脏缺血再灌注损伤有一定的保护作用。     

CRRT联合白蛋白治疗危重症合并急性肾衰竭的疗效观察

目的:探讨CRRT联合白蛋白治疗危重症合并急性肾衰竭的临床疗效。方法:选择我院2016年8月~2018年7月间收治的危重症合并急性肾衰竭患者84例,随机分为对照组和观察组,各42例。观察组采用24h CRRT联合人血白蛋白治疗,对照组采用CRRT治疗,比较两组治疗前后ALB、BUN、SCr、IL-6、K+变化及并发症发生率情况。结果:治疗前,两组ALB、BUN、SCr、IL-6及K+水平比较差异无统计学意义(P>0.05);治疗后,两组ALB水平均升高,BUN、SCr、IL-6及K+水平均降低(P<0.05);观察组治疗后ALB水平高于对照组,BUN、SCr、K+水平低于对照组(P<0.05),两组IL-6水平比较无明显差异(P>0.05);观察组急性ARDS、多器官出血、渗出性肺炎发生率明显低于对照组(P<0.05)。结论:CRRT联合白蛋白对维持危重症并急性肾衰竭患者水电解质平衡、改善肾功能及降低临床并发症方面的疗效显著,可临床推广应用。     

降钙素基因相关肽和内皮素在大鼠急性肾衰竭中的变化及作用

目的:研究降钙素基因相关肽(CGRP)对急性肾衰竭(ARF)的影响,探讨CGRP和内皮素-1(ET-1)在ARF中的变化和作用.方法:采用肌内注射甘油法复制ARF大鼠模型,将大鼠随机分成实验组、治疗组及对照组,动态观察各组动物肾功能指标,并用放射免疫方法检测大鼠不同时相点血浆CGRP、ET-1水平的变化.结果:治疗组大鼠肾功能明显减轻,实验组血浆CGRP水平明显降低(P＜0.05),血浆ET-1水平明显增高(P＜0.01).结论:血浆CGRP、ET-1含量测定可以作为反映肾功能状态和分析ARF病程发展与转归的敏感指标,CGRP对ARF时的肾脏有保护作用.