Effect of bee venom and its melittin on apical transporters of renal proximal tubule cells

Renal failure by bee venom may be related to a malfunction of renal transporters. However, the effects of bee venom on apical membrane transporters of renal proximal tubular cells are not yet known. The aim of this study was to examine the effects of dried bee venom of Apis mellifera and its melittin on apical transporter activity of primary cultured rabbit kidney proximal tubule cells. Bee venom (1 microg/ml) decreased the cell viability and increased lactate dehydrogenase activity over 30-min treatments. Its effect was blocked by mepacrine or AACOCF(3) (10(-6) M; phospholipase A(2) inhibitors). However, there was no effect on cell viability at a concentration of 0.01 microg/ml of bee venom. Thus, we investigated the effect of bee venom (1 microg/ml) on the activity of renal transporters at 30 min. Bee venom inhibited alpha-methyl-D-glucopyranoside, Pi, and Na(+) uptakes, but increased Ca(2+) uptake. These effects of bee venom were blocked by mepacrine or AACOCF(3) (10(-6) M), and bee venom-induced stimulation of Ca(2+) uptake was also blocked by methoxyverapamil and nifedipine (L-type calcium channel blockers). In addition, bee venom increased [(3)H]-arachidonic acid release by 216 % of that of control. In all experiments, bee venom melittin (0.5 microg/ml) had an identical effect to that of bee venom itself. In conclusion, bee venom inhibited, in part, alpha-MG, Pi, and Na(+) uptakes through its melittin which increased Ca(2+) uptake and arachidonic acid release in primary cultured rabbit renal proximal tubule cells.     

High glucose inhibits glucose uptake in renal proximal tubule cells by oxidative stress and protein kinase C

BACKGROUND: High glucose has been considered to play an important role in alteration of renal proximal tubule transporter's activity. This study examined the mechanism by which high glucose modulates alpha-methyl-D-glucopyranoside (alpha-MG) uptake in primary cultured rabbit renal proximal tubule cells (PTCs). METHODS: PTCs were incubated with 25 mmol/L glucose alone or combined with taurine, ascorbic acid, catalase, staurosporine, and bisindolylmaleimide I. Then alpha-MG uptake and lipid peroxide (LPO) formation were examined. RESULTS: Twenty-five mmol/L glucose from four hours, but not 25 mmol/L mannitol, inhibited alpha-MG uptake by 23% compared with 5 mmol/L glucose (control). In the study to examine the relationship of oxidative stress in the high-glucose-induced inhibition of alpha-MG uptake, 25 mmol/L glucose significantly increased LPO by 27% compared with control. However, 10 mmol/L glucose did not affect alpha-MG uptake and LPO formation. Taurine (2 mmol/L), ascorbic acid (1 mmol/L), endogenous antioxidants, or catalase (600 U/mL) significantly blocked 25 mmol/L glucose-induced increase of LPO formation and inhibition of alpha-MG uptake. In the experiment to examine the effects of protein kinase C on LPO formation, 12-O-tetradecanoylphorbol-13-acetate (TPA; 100 ng/mL) increased LPO formation, and staurosporine (10(-7) mol/L) and bisindolylmaleimide I (10(-6) mol/L) totally blocked 25 mmol/L glucose-induced increase of LPO formation and inhibition of alpha-MG uptake. In addition, taurine reduced TPA-induced increase of LPO formation and inhibition of alpha-MG uptake. CONCLUSION: High glucose induces, in part, the inhibition of alpha-MG uptake through LPO formation, and activation of protein kinase C may play a role in high-glucose-induced LPO formation in the primary cultured rabbit renal PTCs.     

Epidermal growth factor regulates Ca2+ uptake in primary cultured renal proximal tubule cells: involvement of cAMP,PKC and cPLA2

Epidermal growth factor (EGF) is known to play an important role in modulating renal transport functions. Thus, we investigated the effect of EGF on Ca(2+) uptake and its related signals in the primary cultured rabbit renal proximal tubule cells. EGF (50 ng/ml, 1 h) stimulated Ca(2+) uptake. Its effect was blocked by AG 1478 (an EGF receptor antagonist), genistein or herbimycin A (tyrosine kinase inhibitors). EGF increased intracellular cAMP level and SQ 22536 (an adenylate cyclase inhibitor), Rp-cAMP (a cAMP analogue), or PKI (a protein kinase A inhibitor) blocked the EGF-induced stimulation of Ca(2+) uptake. EGF-induced stimulation of Ca(2+) uptake was also blocked by neomycin or U-73122 (phospholipase C inhibitors), staurosporine, H-7, or bisindolylmaleimide I (protein kinase C inhibitors), nifedipine or methoxyverapamil (L-type Ca(2+) channel blockers). It increased IPs formation by 167 +/- 5% compare to control within 90 s. On the other hand, EGF increased [(3)H]-arachidonic acid release, which was significantly blocked by PKC inhibitors. In addition, PGE(2), one of cyclooxygenase metabolites, and 5,6-EET, one of cytochrome P-450 metabolites, increased Ca(2+) uptake. These results suggest that cAMP, PLC/PKC, and PLA(2) are involved in EGF-induced stimulation of Ca(2+) uptake.     

Hepatic alpha 2 mu-globulin localizes to the cytosol of rat proximal tubule cells

BACKGROUND: Alpha 2 mu-Globulin (A2), an 18.6 kD protein of hepatic origin, accumulates in the proximal tubule as an abundant, 15.5 kD cleavage product termed "A2-fragment" (A2-f). A2-f facilitates proximal tubule fatty acid oxidation, presumably by binding hydrophobic ligands. This requires some A2-f to enter the cytosol of the renal epithelial cell (REC). The localization of A2/A2-f in the proximal tubule cell was evaluated in this study. METHODS: Immunoblot analysis of renal cortical homogenates separated by differential centrifugation and quantitative immunoelectron microscopy (IEM) was performed to localize A2/A2-f using an affinity-purified antibody that detects both proteins. To evaluate A2 as a physiologically relevant ligand, the accumulation of A2-f in the female rat kidney (normally devoid of A2-f) was examined after the induction of hepatic A2 synthesis. Ligand binding, uptake, and degradation assays were used to assess A2 processing by RECs in vitro. RESULTS: Although A2 and A2-f were detected in the "lysosomal" fraction, only A2-f was found in the soluble protein fraction. IEM confirmed the presence of significant signal in the vesicular and lysosomal as well as the cytosolic compartments. In contrast, both beta 2 mu globulin (B2) and cathepsin B were restricted to endosomes. In the female rat, induction of hepatic A2 production resulted in A2-f accumulation in the renal cortex. In RECs in culture, uptake of A2 and B2 demonstrated nonsaturable, nondisplacable surface binding and similar uptake rates. Compared with B2, A2 was markedly resistant to degradation. CONCLUSIONS: A fraction of A2 escapes lysosomal degradation, permitting A2-f to accumulate in the cytosol of the proximal tubule epithelial cell. A2 may represent an unusual example of a physiologic protein capable of accumulating in a distant cell type.     

Ginsenosides protect apical transporters of cultured proximal tubule cells from dysfunctions induced by h(2)o(2)

Oxidative stress has been implicated as a primary cause of renal failure in certain renal diseases. Indeed, renal proximal tubule is a very sensitive site to oxidative stress and retains functionally fully characterized transporters. It has been reported that ginsenosides have a beneficial effect on diverse diseases including oxidative stress. However, the protective effect of ginsenosides on oxidative stress has not been elucidated in renal proximal tubule cells. Thus, we examined the effect of ginsenosides on oxidative stress-induced alteration of apical transporters and its related mechanism in renal proximal tubule cells. In the present study, hydrogen peroxide (H(2)O(2)) (>10(-5) M) inhibited alpha-methyl-D-glucopyranoside uptake in a dose-dependent manner (p < 0.05). It also inhibited Pi and Na(+) uptake. At a concentration of 20 microg/ml, total ginsenosides significantly reduced H(2)O(2)-induced inhibition of apical transporters. In contrast, protopanaxadiol (PD) and protopanaxatriol (PT) saponins exhibited a less preventive effect than total ginsenosides (p < 0.05). Furthermore, we examined its action mechanism. H(2)O(2) increased lipid peroxide formation, arachidonic acid (AA) release, and Ca(2+) uptake. These effects on H(2)O(2) were significantly prevented by total ginsenosides and PD or PT sanponins. However, total ginsenosides appear to be more protective than PD and PT saponins (p < 0.05). In conclusion, ginsenosides prevented H(2)O(2)-induced inhibition of apical transporters via a decrease in oxidative stress, AA release, and Ca(2+) uptake in primary cultured renal proximal tubule cells.     

肾脏64层螺旋CT灌注成像对梗阻性肾积水患者患肾功能的评价

目的 探讨64层螺旋CT灌注成像检查对梗阻性肾积水患者患肾功能的评估价值.方法 梗阻性肾积水患者36例行64层螺旋CT灌注扫描和肾动态显像(SPECT)测定单侧GFR.其中有肾积水表现者48侧(积水组),28例健康志愿者作为正常对照1组,比较2组各灌注参数值.根据GFR结果将36例患者72侧肾脏分为正常对照2组、肾功能轻度受损组、重度受损组,比较3组肾皮质和髓质血流灌注参数的差异;将各灌注参数与单侧肾脏GFR行Pearson相关性分析. 结果 ①36例患者CT灌注成像表现为双侧时间密度曲线(TDC)不对称,积水组肾皮质、髓质TDC斜率与峰高降低.积水肾皮质血流量(BF)为(203.2±44.9)ml·100 ml~(-1)·min~(-1),血容量(BV)为(27.6±3.9)ml/100 ml,表面通透性(PS)为(30.7±6.5)ml·100 ml~1·min~(-1),Patlak血容量(PBV)为(46.5±10.9)ml/100ml;肾髓质分别为(99.9±24.1)ml·100 ml~(-1)·min~(-1)、(18.3±4.3)ml/100 ml、(51.8±12.1)ml·100 ml~(-1)·min~(-1)、(21.3±3.0)ml/100 ml.与对照1组肾皮质的(301.6±68.8)ml·100 ml~(-1)·min~(-1)、(38.9±5.8)ml/100 ml、(42.9±10.9)ml·100 ml~(-1)·min~(-1)、(67.5±10.3)ml/100 ml及肾髓质的(157.8±34.6)ml·100 ml~(-1)·min~(-1)、(28.5±3.9)ml/100 ml、(75.6±22.7)ml·100 ml~(-1)·min~(-1)、(28.2±0.9)ml/100 ml比较,灌注参数值均下降,差异均有统计学意义(P值均<0.05).②对照2组肾皮髓质BF、BV、PS、PBV分别为(31 4.2±28.7)ml·100 ml~(-1)·min~(-1)、(39.7±2.2)ml/100 ml、(45.2±3.4)ml·100 ml~(-1)·min~1、(68.6±4.3)ml/100 ml和(161.2±10.4)ml·100 ml~(-1)·min~(-1)、(28.7±1.8)ml/100 ml、(80.1±6.7)ml·100 ml~(-1)·min~(-1)、(27.9±6.9)ml/100 ml;肾功能轻度受损组分别为(245.8±16.8)ml·100 ml~(-1)·min~(-1)、(30.5±3.2)ml/100ml、(34.7±5.7)ml·100 ml~(-1)·min、(54.9±7.2)ml/100 ml和(120.7±1 9.6)ml·100 ml~1·min~(-1)、(22.0±2.7)ml/100 ml、(61.9±10.5)ml·100 ml~(-1)·min~(-1)、(23.0±2.2)ml/100 ml;肾功能重度受损组分别为(170.1±29.0)ml·100 ml~(-1)·min~(-1)、(25.4±2.8)ml/100 ml、(27.5±5.2)ml·100 ml~(-1)·min~(-1)、(40.0±8.4)ml/100 m1和(83.7±11.5)ml·100 ml~(-1)·min~(-1)、(15.5±2.9)ml/100 ml、(44.0±5.8)ml·100 ml~(-1)·min~(-1)、(20.0±2.8)ml/100 ml.3组间肾皮髓质血流灌注参数比较差异均有统计学意义(P<0.05).③肾皮髓质各灌注参数与GFR有良好的相关性.其中肾皮质BF相关性最好,r=0.852. 结论 64层螺旋CT肾脏灌注成像可对积水肾肾皮髓质血流灌注状态与肾功能损害进行定量评估,对受损肾功能可进行分级诊断,测定的肾皮髓质各灌注参数值与GFR有良好的相关性.     

Digoxin-like immunoreacting substance(s) in the serum of patients with chronic uremia

In patients with chronic uremia we have previously demonstrated a significant inhibition of the Na-K-ATPase enzyme which represents the specific receptor protein for cardiac glycosides. Since an endogenous inhibitor of this enzyme was previously shown to react with a digoxin antibody, in the present study we determined digoxin-like immunoreacting activity(ies) (DLIA) by a radioimmunoassay in 15 nondialyzed patients with chronic renal failure. In native serum, DLIA ranged from 0 to 1.70 ng/ml and was unrelated to the degree of renal failure. After gel filtration of serum, DLIA exclusively eluted in the small molecular weight salt (FIII) and post-salt (FIV) fractions and averaged 0.22 +/- 0.04 and 0.20 +/- 0.05 ng/ml in fractions III and IV, respectively. Total activities ranged from 0.11 to 0.88 ng/ml with a mean of 0.42 +/- 0.06 ng/ml and closely correlated with the degree of renal impairment (p less than 0.001). The results confirm the presence of small molecular weight digoxin-like immunoreacting substance(s) in uremic serum. The variable activities in native serum and the lack of correlation between the degree of renal failure and DLIA in serum fraction IV previously shown to possess the Na-K-ATPase-inhibiting activity, however, indicate that DLIA may not reflect specifically the endogenous sodium pump inhibitor and that unspecific binding to this digoxin antibody of uremic toxins or other endogenous compounds, such as steroids other than aldosterone, may have occurred.     

In vitro cyclosporine toxicity. The effect of verapamil

The epithelial cell line LLC-PK1, which expresses many proximal tubular characteristics, was used to investigate the relationship between calcium, the calcium channel blocker verapamil, and cyclosporine toxicity. The LLC-PK1 cells took up cyclosporine when this was added in a concentration of 2 micrograms/ml, and this uptake was maximal at 30 min (112 +/- 3 ng cyclosporine/mg cell protein). At 12 micrograms/ml it inhibited the sodium glucose cotransporter, as assessed by phlorizin-inhibitable 14C-alpha-methyl glucopyranoside (alpha-MG) uptake (control 37.2 +/- 6.3, 12 micrograms/ml 21.2 +/- 1.1 mumol/hr/mg protein). Cyclosporine at 2 micrograms/ml did not affect cell growth after 5 days (control 945 +/- 60 micrograms cell protein per 25 cm2 flask, 2 micrograms/ml cyclosporine/ml 1046 +/- 32 micrograms protein/flask), even in the presence of 7.6 mM ionized calcium (862 +/- 37 micrograms protein/flask). Cyclosporine at 12 micrograms/ml inhibited cell growth (286 +/- 27 micrograms protein/flask), and raising the ambient ionized calcium concentration to 7.6 mM reduced cell growth further (91 +/- 6 micrograms protein/flask). Cyclosporine at concentrations of 2 and 12 micrograms/ml produced increasing cell vacuolation, as seen in vivo. Short-term uptake of 2 micrograms/ml cyclosporine could be inhibited by 1.0 mM and 0.5 mM verapamil (49 +/- 9.5 and 71 +/- 6.4 ng cyclosporine/mg cell protein, respectively, at 30 min). However, in the presence of 2 micrograms/ml cyclosporine 0.1 mM verapamil was toxic to the cells grown over five days (44 +/- 5 micrograms protein/flask). At 0.01 mM verapamil was not toxic to cell growth (921 +/- 29 micrograms protein/flask), but raising the medium calcium to 7.6 mM reduced cell growth (652 +/- 96 micrograms/ml). Inhibition of cyclosporine uptake did not occur with 0.01 mm verapamil (control 145.6 +/- 12.3 vs. 0.01 mM verapamil 150.4 +/- 3.8 ng cyclosporine/mg cell protein). The LLC-PK1 cell line represents a good in vitro model for cyclosporine renal tubular toxicity, as the in vivo observation of glycosuria and proximal tubular cell vacuolation in cyclosporine nephrotoxicity can be reproduced. In vitro this is shown to be associated with inhibition of sodium-dependent glucose cotransport. Verapamil inhibited cyclosporine uptake, but only at concentrations that were toxic to the cells. Verapamil potentiated rather than reduced the increased cyclosporine toxicity produced by increasing the medium calcium concentration. The suggested protective effect of verapamil against cyclosporine nephrotoxicity is therefore unlikely to be due to inhibition of cyclosporine uptake or of calcium entry into proximal tubular cells.     

MEPE has the properties of an osteoblastic phosphatonin and minhibin

Matrix extracellular phosphoglycoprotein (MEPE) is expressed exclusively in osteoblasts, osteocytes and odontoblasts with markedly elevated expression found in X-linked hypophosphatemic rickets (Hyp) osteoblasts and in oncogenic hypophosphatemic osteomalacia (OHO) tumors. Because these syndromes are associated with abnormalities in mineralization and renal phosphate excretion, we examined the effects of insect-expressed full-length human-MEPE (Hu-MEPE) on serum and urinary phosphate in vivo, (33)PO(4) uptake in renal proximal tubule cultures and mineralization of osteoblast cultures. Dose-dependent hypophosphatemia and hyperphosphaturia occurred in mice following intraperitoneal (IP) administration of Hu-MEPE (up to 400 microg kg(-1) 31 h(-1)), similar to mice given the phosphaturic hormone PTH (80 microg kg(-1) 31 h(-1)). Also the fractional excretion of phosphate (FEP) was stimulated by MEPE [65.0% (P < 0.001)] and PTH groups [53.3% (P < 0.001)] relative to the vehicle group [28.7% (SEM 3.97)]. In addition, Hu-MEPE significantly inhibited (33)PO(4) uptake in primary human proximal tubule renal cells (RPTEC) and a human renal cell line (Hu-CL8) in vitro (V(max) 53.4% inhibition; K(m) 27.4 ng/ml, and V(max) 9.1% inhibition; K(m) 23.8 ng/ml, respectively). Moreover, Hu-MEPE dose dependently (50-800 ng/ml) inhibited BMP2-mediated mineralization of a murine osteoblast cell line (2T3) in vitro. Inhibition of mineralization was localized to a small (2 kDa) cathepsin B released carboxy-terminal MEPE peptide (protease-resistant) containing the acidic serine-aspartate-rich motif (ASARM peptide). We conclude that MEPE promotes renal phosphate excretion and modulates mineralization.     

Definitions of biochemical failure that best predict clinical failure in patients with prostate cancer treated with external beam radiation alone: a multi-institutional pooled analysis

PURPOSE: Pooled data on 4,839 patients with T1-2 prostate cancer treated with external beam radiation therapy (RT) alone at 9 institutions have previously provided long-term biochemical failure (BF) and clinical outcomes using the American Society for Therapeutic Radiology and Oncology (ASTRO) definition. In this report we determined the sensitivity and specificity of several BF definitions using distant failure (DF) alone or clinical failure (CF), defined as local failure (LF) and/or DF. MATERIALS AND METHODS: The pooled cohort was treated between 1986 and 1995 with external beam RT (60 Gy or greater) without pre-RT androgen suppression or planned post-RT adjuvant androgen suppression. Median followup was 6.3 years. The sensitivity and specificity of 102 definitions of BF relative to DF and LF were assessed. RESULTS: The BF definitions with higher sensitivity and specificity than the ASTRO definition for DF only and CF are reported. The sensitivity and specificity of the ASTRO definition to predict DF alone was 55% and 68%, respectively. Three definitions had higher sensitivity and specificity, namely prostate specific antigen (PSA) greater than current nadir (lowest PSA prior to current measurement) plus 3 ng/ml (sensitivity 76% and specificity 72%), dated at the call (failure date as the date when the criterion was met), PSA greater than absolute nadir plus 2 ng/ml (sensitivity 72% and specificity 70%), dated at the call, or 2 consecutive increases of at least 0.5 ng/ml, back dated (sensitivity 69% and specificity 73%). The sensitivity and specificity of the ASTRO definition to predict CF was 60% and 72%, respectively. Three definitions had higher sensitivity and specificity, namely PSA greater than current nadir plus 3 ng/ml (sensitivity 66% and specificity 77%), dated at the call, PSA greater than absolute nadir plus 2 ng/ml (sensitivity 64% and specificity 74%), dated at the call, or 2 consecutive increases of at least 0.5 ng/ml, back dated (sensitivity 67% and specificity 78%). CONCLUSIONS: Using what is to our knowledge the largest data set of patients with prostate cancer treated with RT alone we correlated multiple definitions of BF with the strict clinical end points of DF alone and CF (DF or local failure). Defining BF as PSA greater than absolute nadir plus 2 ng/ml, dated at the call, PSA greater than current nadir plus 3 ng/ml, dated at the call, or 2 consecutive increases of at least 0.5 ng/ml, back dated, had higher sensitivity and specificity for DF alone or CF compared with the ASTRO definition. This information should contribute to the discussion regarding suggested modifications to the ASTRO definition of biochemical failure.     

Has blood volume an impact on serum PSA levels?

Purpose

Prostate-specific antigen (PSA) is measured in circulating blood volume (BV), which is known to have a wide inter- and intraindividual variability. As data investigating the potential impact of different BV on PSA test validity are scant, we determined the relationship between BV and serum PSA values.

Methods

Men aged 41–60 years, participating in a health screening project, were evaluated. Serum samples of fasting patients were drawn between 8.00 and 10.00 a.m., all PSA measurements were determined in the same laboratory. Circulating BV was calculated according to the Retzlaff formula based on height, weight and haematocrit.

Results

A total of 400 men with a mean age of 47.9 years entered the analysis. Mean PSA was 1.20 ng/ml (range 0.23–8.59 ng/ml) and mean BV was 3,370 ml (range 2,380–4,220 ml). Mean PSA values stratified from lowest to the highest third of BV were 1.22, 1.17 and 1.19 ng/ml in the total cohort. The respective figures for men aged 41–50 years were 1.08, 0.98 and 1.03 ng/ml, and for those aged 51–60 years: 1.47, 1.48 and 1.53 ng/ml. Neither BV nor three other related biometrical parameters (body mass index, waist–hip ratio, body fat percentage) revealed a correlation with the PSA values.

Conclusion

Our data suggest that BV does not have a significant impact on serum PSA values. To exclude a potential minor impact of BV on PSA, larger study cohorts, however, are required.     

High glucose stimulates Ca2+ uptake via cAMP and PLC/PKC pathways in primary cultured renal proximal tubule cells

Alteration of [Ca2+]i by hyperglycemia is implicated in the pathogenesis of diabetic nephropathy. However, the effect of high glucose on Ca2+ regulation in proximal tubule cells is not known. Thus, we examined the mechanisms by which high glucose regulates Ca2+ uptake in primary cultured rabbit renal proximal tubule cells. Glucose increased the Ca2+ uptake in a time- and dose-dependent manner. A stimulatory effect of high glucose on Ca2+ uptake is predominantly observed using 25 mM glucose (high glucose) after 1 h, while 25 mM glucose did not affect cell viability and lactate dehydrogenase release. However, 25 mM mannitol and L-glucose did not affect Ca2+ uptake as compared with controls. Nifedipine and methoxyverapamil (L-type Ca2+ channel blockers) blocked high-glucose-induced stimulation of Ca2+ uptake. High-glucose-induced stimulation of Ca2+ uptake was blocked by pertussis toxin, SQ-22536 (adenylate cyclase inhibitor), myristoylated amide 14-22 (protein kinase A inhibitor), neomycin and U-73122 (phospholipase C inhibitors), and staurosporine and bisindolylmaleimide I (protein kinase C inhibitors). In addition, KN-62 (a Ca2+/calmodulin-dependent protein kinase II inhibitor) and W-7 (a Ca2+/calmodulin antagonist) blocked high-glucose-induced stimulation of Ca2+ uptake. In conclusion, high glucose stimulates the Ca2+ uptake through L-type Ca2+ channels via G-protein-coupled adenylate cyclase/cAMP and phospholipase C/protein kinase C pathways.     

Retention and distribution of polygeline (Haemaccel®) in the rat

The plasma substitute polygeline (Haemaccel®) contains a large fraction of molecules sufficiently small to cross the capillary and glomerular membranes. Plasma volume expansion, tissue extravasation and renal elimination of this artificial colloid were quantified using ¹²⁵l-labelled polygeline molecules. In pentobarbital anaesthetized rats, either 10 ml 3.5% polygeline (n=8) or 10 ml 0.9% saline (n=8) was infused intravenously over 60 min. The plasma volume was assessed by the 3 min distribution volume for ¹³¹l-albumin and the plasma volume changes over time were calculated from erythrocyte volume fractions. The plasma volume increased by 4.6 (2.0) ml (mean (SD)) at the end of the Haemaccel infusion compared with 2.1 (1.8) ml after the saline infusion (P=0.02). One hour later the increase was 2.4 (1.5) and 1.6 (1.0) ml respectively, not significantly different (P=0.20). Extravasation of labelled polygeline was greatest in the kidney, possibly due to cellular uptake. Skin and skeletal muscle contained 4–5 times more polygeline than could be attributed to intravascular radioactivity, but still uptake in these tissues did not reach one percent of the amount injected. Following a 60 min infusion and a 60 min interval, 23 (4)% of the polygeline was recovered intravascularly, 43 (9)% had been excreted in urine, leaving 33% to other compartments. Thus, more polygeline was distributed to the interstitium than remained in the circulation. This calls for further investigations into the handling and effect of polygeline in this extravascular compartment.     

肾细胞癌灌注CT表现与微血管密度及血管内皮生长因子表达的相关性

目的 探讨肾细胞癌的多层螺旋灌注CT表现及其与微血管密度(MVD)、血管内皮生长因子(VEGF)表达的相关性. 方法 经手术病理确诊的肾细胞癌73例,其中透明细胞癌65例、乳头状腺癌3例、嫌色细胞癌5例.术前行多层螺旋灌注CT扫描,分别测量肾癌病灶血容量(BV)、血流量(BF)、平均通过时间(MTT)和毛细血管表面通透性(PS).免疫组化染色检查肾癌组织中MVD及VEGF表达.并与灌注扫描各参数进行相关性分析. 结果 肾癌病灶BV、BF、MTT及PS分别为(17.2±8.3)ml/100g,(262±176)ml·min-1·100g-1、(7.1±3.4)s、(25±13)ml·min-1·100g-1.MVD为7.6～96.3(42.3±21.0);VEGF表达阳性38例(52.1%),其中Ⅰ级24例(32.9%)、Ⅱ级10例(13.7%)、Ⅲ级4例(5.5%).MVD与VEGF无相关性.肾癌病灶MVD与BV、BF、PS呈正相关(P<0.01),与MTT呈负相关(P<0.05);VEGF与所有灌注参数均不相关.结论肾癌灌注CT扫描参数可反映肿瘤组织中的血管生成情况.     

Relationship between energy requirements for Na+ reabsorption and other renal functions

In the mammalian kidney, the use of the ratio, delta net T-Na+/delta Q-O2, provides an overestimate of the energy requirements for unidirectional active Na+ transport. In the proximal tubule, the overestimate of the energy cost for T-Na+ is due to these phenomena: (1) The "leaky" characteristics of the proximal tubule does not permit an accurate estimate to be made of the active fraction of the unidirectional flux of Na+. Thus, the net Na+ or net HCO3- reabsorption rate alone cannot be used to determine the stoichiometry for unidirectional extrusion of Na+ (with HCO3-) by the Na,K-ATPase, since backflux of HCO3- into the lumen occurs. (2) There is a moiety of active Na+ with Cl- along the pars recta. Whether this reabsorptive rate is altered and O2 uptake also changed when GFR or NaHCO3 reabsorption is varied is not yet known. (3) The occurrence of energy-requiring synthetic functions (substrate-interconversions) in the proximal tubule, coupled, in part, to the rate of Na+ entry into the proximal tubule cells, results in changes in renal O2 uptake proportional to some (undetermined) fraction of the change in Na+ reabsorption. The utilization of a portion of these reabsorbed substrates in endergonic syntheses must account for a portion of the Na+-stimulated suprabasal O2 uptake rate. Hence, the presence of synthetic functions in the proximal tubule also contributes to the overestimation of the energy value of net Na+ reabsorption when the ratio, delta net TNa-+/delta Q-O2, is used.(ABSTRACT TRUNCATED AT 250 WORDS)     

Variable definitions influence the reporting of biochemical failure rates

The purpose of this study was to assess how the reporting of biochemical failure (BF) rates would be affected by the application of three different definitions. Three hundred and fifteen men with localized prostate cancer underwent I-125 brachytherapy (n=109), conformal three-dimensional radiation therapy (n=99), or radical prostatectomy (n=107). No patient received adjuvant or neoadjuvant hormone therapy in this study. BF rates at 12, 24 and 36 months were assessed using three definitions: (1) prostate-specific antigen (PSA) nadir >0.5 ng/ml; (2) PSA rise by 0.5 ng/ml; and (3) three consecutive PSA rises. Median follow-up for the brachytherapy group, external beam radiotherapy group, and the radical prostatectomy group was 27, 30 and 36 months respectively. The applied definition influenced reporting of failure rates in two of the three groups. I-125 brachytherapy group: BF rates at 24 months: 46%-definition 1, 35%-definition 2, and 4%-definition 3 (P<0.05). Radiation therapy group: BF rates at 24 months: 39%-definition 1, 17%-definition 2 and 3%-definition 3 (P<0.05). No patient in the radical prostatectomy group had a BF by any applied definition. A more universal definition of BF is needed to compare the efficacy of treatments for localized prostate cancer.     

Decreased phospholipase A2 activity in plasma and liver in uncontrolled diabetes mellitus. A defect in the early steps of prostaglandin synthesis?

Arachidonic acid metabolites and prostaglandins participate in numerous physiologic functions. An enzyme important in the control of prostaglandin production is phospholipase A2. In this study, we have investigated the changes in plasma and hepatic phospholipase A2 activity in diabetes mellitus. In uncontrolled diabetic patients, the postheparin plasma phospholipase A2 level was 18.7 +/- 4.1 U/ml; this value was significantly different from the enzyme activities in control subjects (106 +/- 9.8 U/ml) and in controlled diabetic patients (87 +/- 7.3 U/ml). In the streptozocin-induced diabetic rat model, the postheparin plasma phospholipase A2 level (1.9 +/- 0.45 U/ml) was also decreased when compared with normal (9.4 +/- 1.6 U/ml) and controlled diabetic rats (7.0 +/- 1.3 U/ml). The total hepatic enzyme activity in the uncontrolled diabetic rats was only 21.6% of that seen in control rats. Subcellular fraction studies demonstrated that the enzyme activity is decreased in all fractions in the liver. Liver perfusion studies showed that the heparin-releasable phospholipase A2 activity in the perfusate was significantly decreased in the diabetic rats when compared with control and controlled diabetic animals. We conclude that postheparin plasma and hepatic phospholipase A2 activities are decreased in uncontrolled diabetes mellitus, that the low plasma activity is related to decreased release from the liver, and that the alterations in phospholipase A2 activity in plasma and liver are restored to normal by controlling the diabetic status.     

Effect of haemodialysate and its peptide fractions on lactate dehydrogenase activity in erythrocytes from healthy subjects and patients with end-stage renal disease

The effect of haemodialysate and its 3 peptide fractions on lactate dehydrogenase activity in erythrocytes was studied in patients treated by repeated haemodialysis for end-stage renal disease and in healthy subjects. Erythrocytes from dialyzed patients showed significantly lower LDH activity than those from healthy subjects. After a 3-h incubation with haemodialysate (675 and 450 μg protein/ml) or its peptide fraction III (270 and 190 μg protein/ml), a significant inhibition of LDH activity was observed. On the other hand, neither haemodialysate nor its peptide fractions inhibited LDH activity in red blood cells from patients with end-stage renal disease treated by repeated haemodialysis.     

Contribution of angiotensin II to late renal injury after acute ischemia

Rats recovering from acute renal ischemia exhibit tubule loss and interstitial fibrosis followed by development of proteinuria and glomerular sclerosis. The current study assessed the contribution of angiotensin II (AngII) to these processes. The contribution of AngII to early tubule loss and interstitial fibrosis was assessed in rats studied for 35 d after right nephrectomy and transient occlusion of the left renal artery. One group of rats received no treatment, while a second group received losartan beginning at 2 d following ischemia. Studies at 35 d showed that losartan did not improve GFR (2.04 +/- 0.30 ml/min treated, 2.16 +/- 0.21 ml/min untreated), reduce the fraction of glomeruli that were no longer connected to normal tubule segments (42 +/- 9% treated, 42 +/- 13% untreated), or limit expansion of the interstitial volume fraction (25 +/- 3% treated, 25 +/- 4% untreated). The contribution of AngII to progressive glomerular injury following initial recovery from ischemia was assessed in similarly prepared rats studied for 140 d. One group of rats received no treatment, while a second group received enalapril beginning at 35 d following ischemia. Enalapril markedly reduced proteinuria (78 +/- 17 mg/d treated, 229 +/- 52 mg/d untreated) and the prevalence of segmental glomerular sclerosis (14 +/- 9% treated, 45 +/- 10% untreated). Untreated rats developed sclerotic lesions in glomeruli not connected to normal tubules, as well as in glomeruli connected to normal tubules. Enalapril prevented injury in both classes of glomeruli. These results indicate that AngII does not contribute to interstitial fibrosis during recovery from ischemic injury. Reduction of AngII activity, can, however, prevent secondary glomerular injury in kidneys initially damaged by ischemia.