坎地沙坦对大鼠输尿管梗阻后肾脏功能和Na-K-2Cl共转运蛋白2表达的影响

目的 观察坎地沙坦干预对双侧输尿管梗阻(BUO)大鼠肾功能和Na-K-2Cl共转运蛋白2( NKCC2)的影响.方法 30只大鼠随机分为假手术(Sham)、BUO和坎地沙坦干预组(BUO+CAN).BUO组和(BUO+ CAN)组均行BUO手术,(BUO+ CAN)组坎地沙坦干预,24h后解除梗阻再观察48 h收集血液、肾脏标本.免疫印迹实验检测肾脏NKCC2表达水平.结果 梗阻解除后BUO与Sham组比较尿量、尿Na增高[(99±6) μl/(min·kg)比(28±4)μl/(min·kg)]和[(7.0±0.7) μmol/(min·kg)比(4.0±0.4) μmol/(min·kg)],尿渗透压降低,血浆渗透压、醛固酮升高.BUO +CAN与BUO组比较尿量、尿Na降低[(60±7)μl(min·kg)比(99±6)μl(min·kg)]和[(4.9±0.4) μmol/( min·kg)比(7.0±0.7)μmol/( min·kg)],尿渗透压增高,血浆渗透压、血浆醛固酮降低.NKCC2表达BUO组下降到Sham组的24％,(BUO+CAN)组高于BUO组[(58±6)％比(24±7)％].各组比较差异均有统计学意义(P＜0.05).结论 坎地沙坦可阻止BUO后NKCC2下调,纠正代谢紊乱,保护肾功能.     

Increased expression of sodium transporters in rats chronically inhibited of nitric oxide synthesis

The present study was done to determine whether endogenous nitric oxide (NO) plays a role in the regulation of sodium transporters in the kidney. Male Sprague-Dawley rats were treated with NG-nitro-L-arginine methyl ester (L-NAME, 100 mg/L drinking water) for 4 weeks. Control rats were supplied with tap water without drugs. Expression of Na, K-ATPase, type 3 Na/H exchanger (NHE3), Na/K/2Cl cotransporter (BSC1), and thiazide-sensitive Na/Cl cotransporter (TSC) proteins was determined in the kidney by Western blot analysis. Catalytic activity of Na,K-ATPase was also determined. The treatment with L-NAME significantly and steadily increased the systemic blood pressure. Total and fractional excretion of urinary sodium decreased significantly, while creatinine clearance remained unaltered. Neither plasma renin activity nor aldosterone concentration was significantly altered. The alpha1 subunit expression and the catalytic activity of Na, K-ATPase were increased in the kidney. The expression of NHE3, BSC1 and TSC was also increased significantly. These results suggest that endogenously-derived NO exerts a tonic inhibitory effect on the expression of sodium transporters, including Na, K-ATPase, NHE3, BSC1, and TSC, in the kidney.     

Altered renal sodium transporter expression in an animal model of type 2 diabetes mellitus

Hemodynamic factors play an important role in the development and/or progression of diabetic nephropathy. We hypothesized that renal sodium transporter dysregulation might contribute to the hemodynamic alterations in diabetic nephropathy. Otsuka Long Evans Tokushima Fatty (OLETF) rats were used as an animal model for type 2 diabetes. Long Evans Tokushima (LETO) rats were used as controls. Renal sodium transporter regulation was investigated by semiquantitative immunoblotting and immunohistochemistry of the kidneys of 40-week-old animals. The mean serum glucose level in OLETF rats was increased to 235+/-25 mg/dL at 25 weeks, and the hyperglycemia continued up to the end of 40 weeks. Urine protein/ creatinine ratios were 10 times higher in OLETF rats than in LETO rats. At 40th week, the abundance of the epithelial sodium channel (ENaC) beta-subunit was increased in OLETF rats, but the abundance of the ENaC gamma-subunit was decreased. No significant differences were observed in the ENaC alpha-subunit or other major sodium transporters. Immunohistochemistry for the ENaC beta-subunit showed increased immunoreactivity in OLETF rats, whereas the ENaC gamma-subunit showed reduced immunoreactivity in these rats. In OLETF rats, ENaC beta-subunit upregulation and ENaC gamma-subunit downregulation after the development of diabetic nephropathy may reflect an abnormal sodium balance.     

Altered cell volume regulation in ras oncogene expressing NIH fibroblasts

Expression of the Ha-ras oncogene has been reported to stimulate the dimethylamiloride sensitive Na⁺/H⁺ exchanger and Na⁺, K⁺, 2Cl^– cotransport, both transport systems which are involved in cell volume regulation. The present study has been performed to test for an influence of ras oncogene expression on cell volume regulation in NIH 3T3 fibroblasts expressing the Ha-ras oncogene (+ ras). As controls served NIH 3T3 fibroblasts not expressing the ras oncogene (– ras). In isotonic extracellular fluid, the cell volume of + ras cells (2.70±0.08 pl) is significantly greater than the cell volume of –ras cells (2.04±0.10 pl). Both, + ras and – ras cells exhibit a regulatory cell volume increase in hypertonic extracellular fluid and a regulatory cell volume decrease in hypotonic extracellular fluid. The regulatory cell volume decrease is inhibited by 1 mmol/l quinidine and barium, the regulatory cell volume increase is inhibited in – ras and + ras cells by dimethyl-amiloride (100 mol/l) and, only in + ras cells, by furosemide (100 mol/l) and bumetanide (10 mol/l). In conclusion, expression of the ras oncogene leads to a shift of the set point for cell volume regulation to greater cell volumes, which may contribute to the activation of the Na⁺/H⁺ exchanger and Na⁺, K⁺, 2Cl^– cotransport.     

Berberine acutely inhibits the digestion of maltose in the intestine

Ethnopharmacological relevance

The Chinese Goldthread Rhizome has been used in the Traditional Chinese Medicine as an important ingredient of many formulas for the treatment of diabetes mellitus. Berberine, the main effective composition of Chinese Goldthread Rhizome, is also effective in treating diabetes in today's clinical practice of Traditional Chinese Medicine.

Aim of the study

To evaluate the hypoglycemic activity of berberine which treats acutely on the postprandial blood glucose, and to explore the mechanism of this activity.

Materials and methods

1. One-dose preprandial intragastric administrations of berberine were given to normal animals (dogs and rats), and the postprandial blood glucose concentration curves were measured. Serum insulin enzyme linked immunosorbent assay (ELISA) was only performed in rats. 2. The euglycemic clamp test was performed to evaluate the effect of one-dose berberine intragastric administration on the blood glucose transformation and utilization rate in rats. 3. In the Caco-2 cell monolayer test, the changes of glucose concentration on the apical and basolateral sides were measured when the maltose solution containing berberine was added to the apical side. 4. The inhibition ratio of berberine against α-glucosidase was measured in vitro. 5. The effect of berberine on the fluorescence emission spectrums of α-glucosidase was studied.

Results

One-dose preprandial intragastric administration of berberine delayed the rise of post-maltose blood glucose, did not affect postprandial blood glucose after glucose meal, and did not affect the insulin level in normal rats; reduced post-maltose blood glucose in normal dogs. 2. The result of euglycemic clamp test showed that one-dose intragastric administration of berberine had no effect on the blood glucose transformation and utilization rate in rats. 3. Berberine added to the maltose solution on the apical side of Caco-2 cell monolayer reduced the glucose concentration on the apical side. Glucose in basolateral side of all groups cannot be detected. 4. Berberine inhibited the activity of α-glucosidase in vitro. 5. Berberine significantly and concentration dependently quenched the fluorescence emission spectrum of α-glucosidase.

Conclusion

Our findings suggest an additional mechanism of the hypoglycemic activity of berberine by demonstrating its ability to acutely inhibit the α-glucosidase, and support the traditional use of berberine and Chinese Goldthread Rhizome for the treatment of diabetes mellitus.     

Functional expressions of endogenous dipeptide transporter and exogenous proton/peptide cotransporter inXenopus oocytes

It is essential to clone the peptide transporter in order to obtain better understanding of its molecular structure, regulation, and substrate specificity. Characteristics of an endogenous peptide transporter in oocytes were studied along with expression of an exogenous proton/peptide cotransporter from rabbit intestine. And further efforts toward cloning the transporter were performed. The presence of an endogenous peptide transporter was detected inXenopus laevis oocytes by measuring the uptake of 0.25 μM (10Ci/ml) [³H]-glycylsarcosine (Gly-Sar) at pH 5.5 with or without inhibitors. Uptake of Gly-Sar in oocytes was significantly inhibited by 25 mM Ala-Ala, Gly-Gly, and Gly-Sar (p<0.05), but not by 2.5 mM of Glu-Glu, Ala-Ala, Gly-Gly, Gly-Sar and 25 mM glycine and sarcosine. This result suggests that a selective transporter is involved in the endogenous uptake of dipeptides. Collagenase treatment of oocytes used to strip oocytes from ovarian follicles did not affect the Gly-Sar uptake. Changing pH from 5.5 to 7.5 did not affect the Gly-Sar uptake significantly, suggesting no dependence of the endogenous transporter on a transmembrane proton gradient. An exogenous H⁺/peptide cotransporter was expressed after microinjection of polyadenylated messenger ribonucleic acid [poly(A)⁺-mRNA] obtained from rabbit small intestine. The Gly-Sar uptake in mRNA-injected oocytes was 9 times higher than that in water-injected oocytes. Thus, frog oocytes can be utilized for expression cloning of the genes encoding intestinal H⁺/peptide cotransporters. Size fractionation of mRNA was successfully obtained using this technique.     

高血磷对5/6肾切除大鼠肾Ⅱa型钠-磷协同转运子基因表达的影响及司维拉姆的干预作用

目的研究高血磷对5/6肾切除大鼠肾脏Ⅱa型钠-磷协同转运子(NaPi-2)mRNA表达的影响及司维拉姆(Renagel)的干预作用。方法42只SD大鼠,随机分为5/6肾切除加高磷饲料组(STNx+HP)(含P1.2%)、5/6肾切除加低磷饲料组(STNx+LP)(含P0.2%)、5/6肾切除加正常磷饲料组(STNx+NP)、5/6肾切除高磷饲料+Renagel组(STNx+HP+Ren)(Renagel在饲料中占2%)、假手术高磷饲料组(Sham+HP)、假手术低磷饲料组(Sham+LP)、假手术正常磷饲料组(Sham+NP)。术后14d,测定血清离子钙(iCa)、磷(P)、全段甲状旁腺激素(iPTH)、血1,25-(OH)2D3和尿磷酸盐排泄分数(FEp)。RT-PCR检测NaPi-2mRNA在肾脏的表达。结果STNx+Hp组的血P、iPTH明显高于STNx+LP组及假手术3个组(P均<0.05);上述5个组间的血iCa、1,25-(OH)2D3差异无统计学意义(P均>0.05)。STNx+LP组血P、iPTH均明显低于STNx+HP组(P均<0.05)。STNx+HP组较STNx+LP组肾NaPi-2mRNA表达明显减少(P<0.01)。STNx+HP+Ren组较STNx+HP组NaPi-2mRNA表达明显增加。结论高磷血症是促进5/6。肾切除大鼠血iPTH增高且不受钙和1,25-(OH)2D3影响的独立因素。高磷显著地降低5/6肾切除鼠肾NaPi-2mRNA表达,而司维拉姆能显著降低血磷及iPTH,增加肾NaPi-2mRNA表达。     

The SLC4 family of HCO3 − transporters

The SLC4 family consists of ten genes. All appear to encode integral membrane proteins with very similar hydropathy plots-consistent with the presence of 10-14 transmembrane segments. At least eight SLC4 members encode proteins that transport HCO(3)(-) (or a related species, such as CO(3)(2-)) across the plasma membrane. Functionally, these eight proteins fall into two major groups: three Cl-HCO(3) exchangers (AE1-3) and five Na(+)-coupled HCO(3)(-) transporters (NBCe1, NBCe2, NBCn1, NDCBE, NCBE). Two of the Na(+)-coupled HCO(3)(- )transporters (NBCe1, NBCe2) are electrogenic; the other three Na(+)-coupled HCO(3)(-) transporters and all three AEs are electroneutral. At least NDCBE transports Cl(-) in addition to Na(+) and HCO(3)(-). Whether NCBE transports Cl(-)-in addition to Na(+) and HCO(3)(-)-is unsettled. In addition, two other SLC4 members (AE4 and BTR1) do not yet have a firmly established function; on the basis of homology, they fall between the two major groups. A characteristic of many, though not all, SLC4 members is inhibition by 4,4'-diisothiocyanatostilbene-2,2'-disulfonate (DIDS). SLC4 gene products play important roles in the carriage of CO(2) by erythrocytes, the absorption or secretion of H(+) or HCO(3)(-) by several epithelia, as well as the regulation of cell volume and intracellular pH.     

The ABCs of solute carriers: physiological, pathological and therapeutic implications of human membrane transport proteins

The Human Genome Organisation (HUGO) Nomenclature Committee Database provides a list of transporter families of the solute carrier (SLC) gene series (see ). Currently, it includes 43 families and 298 transporter genes. This special issue features mini-reviews on each of these SLC families written by the experts in each field. A WEB site has been established () that gives the latest updates for the SLC families and their members as well as relevant links to gene databases and reviews in the literature. A list of all currently known SLC families, a discussion of additional SLC families and family members as well as a brief summary of non-SLC transporter genes is included in this introduction.