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  • 1
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    Altered expression of selected genes in kidney of rats with lithium-induced NDI
    American Physiological Society ; 2005
    In:  American Journal of Physiology-Renal Physiology Vol. 288, No. 6 ( 2005-06), p. F1276-F1289
    Details
    In: American Journal of Physiology-Renal Physiology, American Physiological Society, Vol. 288, No. 6 ( 2005-06), p. F1276-F1289
    Abstract: Lithium treatment is associated with development of nephrogenic diabetes insipidus, caused in part by downregulation of collecting duct aquaporin-2 (AQP2) and AQP3 expression. In the present study, we carried out cDNA microarray screening of gene expression in the inner medulla (IM) of lithium-treated and control rats, and selected genes were then investigated at the protein level by immunoblotting and/or immunohistochemistry. The following genes exhibited significantly altered transcription and mRNA expression levels, and these were compatible with the changes in protein expression. 11β-Hydroxysteroid dehydrogenase type 2 protein expression in the IM was markedly increased (198 ± 25% of controls, n = 6), and immunocytochemistry demonstrated an increased labeling of IM collecting duct (IMCD) principal cells. This indicated altered renal mineralocorticoid/glucocorticoid responses in lithium-treated rats. The inhibitor of cyclin-dependent kinases p27 (KIP) protein expression was significantly decreased or undetectable in the IMCD cells, pointing to increased cellular proliferation and remodeling. Heat shock protein 27 protein expression was decreased in the IM (64 ± 6% of controls, n = 6), likely to be associated with the decreased medullary osmolality in lithium-treated rats. Consistent with this, lens aldose reductase protein expression was markedly decreased in the IM (16 ± 2% of controls, n = 6), and immunocytochemistry revealed decreased expression in the thin limb cells in the middle and terminal parts of the IM. Ezrin protein expression was upregulated in the IM (158 ± 16% of controls, n = 6), where it was predominantly expressed in the apical and cytoplasmic domain of the IMCD cells. Increased ezrin expression indicated remodeling of the actin cytoskeleton and/or altered regulation of IMCD transporters. In conclusion, the present study demonstrates changes in gene expression not only in the collecting duct but also in the thin limb of the loop of Henle in the IM, and several of these genes are linked to altered sodium and water reabsorption, cell cycling, and changes in interstitial osmolality.
    Type of Medium: Online Resource
    ISSN: 1931-857X , 1522-1466
    URL: Article
    DOI: 10.1152/ajprenal.00305.2004
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2005
    detail.hit.zdb_id: 1477287-5
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  • 2
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    Using molecular classification to predict gains in maximal aerobic capacity following endurance exercise training in humans
    American Physiological Society ; 2010
    In:  Journal of Applied Physiology Vol. 108, No. 6 ( 2010-06), p. 1487-1496
    Details
    In: Journal of Applied Physiology, American Physiological Society, Vol. 108, No. 6 ( 2010-06), p. 1487-1496
    Abstract: A low maximal oxygen consumption (V̇o 2max ) is a strong risk factor for premature mortality. Supervised endurance exercise training increases V̇o 2max with a very wide range of effectiveness in humans. Discovering the DNA variants that contribute to this heterogeneity typically requires substantial sample sizes. In the present study, we first use RNA expression profiling to produce a molecular classifier that predicts V̇o 2max training response. We then hypothesized that the classifier genes would harbor DNA variants that contributed to the heterogeneous V̇o 2max response. Two independent preintervention RNA expression data sets were generated ( n = 41 gene chips) from subjects that underwent supervised endurance training: one identified and the second blindly validated an RNA expression signature that predicted change in V̇o 2max (“predictor” genes). The HERITAGE Family Study ( n = 473) was used for genotyping. We discovered a 29-RNA signature that predicted V̇o 2max training response on a continuous scale; these genes contained ∼6 new single-nucleotide polymorphisms associated with gains in V̇o 2max in the HERITAGE Family Study. Three of four novel candidate genes from the HERITAGE Family Study were confirmed as RNA predictor genes (i.e., “reciprocal” RNA validation of a quantitative trait locus genotype), enhancing the performance of the 29-RNA-based predictor. Notably, RNA abundance for the predictor genes was unchanged by exercise training, supporting the idea that expression was preset by genetic variation. Regression analysis yielded a model where 11 single-nucleotide polymorphisms explained 23% of the variance in gains in V̇o 2max , corresponding to ∼50% of the estimated genetic variance for V̇o 2max . In conclusion, combining RNA profiling with single-gene DNA marker association analysis yields a strongly validated molecular predictor with meaningful explanatory power. V̇o 2max responses to endurance training can be predicted by measuring a ∼30-gene RNA expression signature in muscle prior to training. The general approach taken could accelerate the discovery of genetic biomarkers, sufficiently discrete for diagnostic purposes, for a range of physiological and pharmacological phenotypes in humans.
    Type of Medium: Online Resource
    ISSN: 8750-7587 , 1522-1601
    URL: Article
    DOI: 10.1152/japplphysiol.01295.2009
    RVK:
    WA 15000
    RVK:
    XA 52094
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2010
    detail.hit.zdb_id: 1404365-8
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  • 3
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    COX-2 activity transiently contributes to increased water and NaCl excretion in the polyuric phase after release of ureteral obstruction
    American Physiological Society ; 2007
    In:  American Journal of Physiology-Renal Physiology Vol. 292, No. 5 ( 2007-05), p. F1322-F1333
    Details
    In: American Journal of Physiology-Renal Physiology, American Physiological Society, Vol. 292, No. 5 ( 2007-05), p. F1322-F1333
    Abstract: Release of bilateral ureteral obstruction (BUO) is associated with reduced expression of renal aquaporins (AQPs), polyuria, and impairment of urine-concentrating capacity. Recently, we demonstrated that 24 h of BUO is associated with increased cyclooxygenase (COX)-2 expression in the inner medulla (IM) and that selective COX-2 inhibition prevents downregulation of AQP2. In the present study, we tested the hypothesis that COX-2 activity increases in the postobstructive phase and that this increase in COX-2 activity contributes to polyuria and impaired urine-concentrating capacity. We examined the effect of the selective COX-2 inhibitor parecoxib (5 mg·kg −1 ·day −1 via osmotic minipumps) on renal functions and protein abundance of AQP2, AQP3, Na-K-2Cl cotransporter type 2 (NKCC2), and Na-K-ATPase 3 days after release of BUO. At 3 days after release of BUO, rats exhibited polyuria, dehydration and urine and IM tissue osmolality were decreased. There were inverse changes of COX-1 and COX-2 in the IM: COX-2 mRNA, protein, and activity increased, while COX-1 mRNA and protein decreased. Parecoxib reduced urine output 1 day after release of BUO, but sodium excretion and glomerular filtration rate were unchanged. Parecoxib normalized urinary PGE 2 and PGI 2 excretion and attenuated downregulation of AQP2 and AQP3, while phosphorylated AQP2 and NKCC2 remained suppressed. Parecoxib did not improve urine-concentrating capacity in response to 24 h of water deprivation. We conclude that decreased NKCC2 and collapse of the IM osmotic gradient, together with suppressed phosphorylated AQP2, are likely causes for the impaired urine-concentrating capacity and that COX-2 activity is not likely to mediate these changes in the chronic postobstructive phase after ureteral obstruction.
    Type of Medium: Online Resource
    ISSN: 1931-857X , 1522-1466
    URL: Article
    DOI: 10.1152/ajprenal.00394.2006
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2007
    detail.hit.zdb_id: 1477287-5
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  • 4
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    Osmotically relevant membrane signaling complex: association between HB-EGF, β 1 -integrin, and CD9 in mTAL
    American Physiological Society ; 2000
    In:  American Journal of Physiology-Cell Physiology Vol. 279, No. 1 ( 2000-07-01), p. C136-C146
    Details
    In: American Journal of Physiology-Cell Physiology, American Physiological Society, Vol. 279, No. 1 ( 2000-07-01), p. C136-C146
    Abstract: The integral membrane proteins cluster of differentiation-9 (CD9), β 1 -integrin, and heparin-binding epidermal growth factor-like (HB-EGF) exist in association in many cell lines and are linked to intracellular signaling mechanisms. Two of the proteins (CD9 and β 1 -integrin) are induced by hypertonicity, suggesting that their related signaling processes may be relevant to osmotic stress. The validity of this hypothesis rests upon coexpression and physical association between these molecules in nephron segments that are normally exposed to high and variable ambient osmolality. In this work, we show that CD9 and β 1 -integrin are induced in rat kidney medulla after dehydration. Immunohistochemistry and immunoprecipitation studies show that CD9, HB-EGF, and β 1 -integrin are coexpressed and physically associated in medullary thick ascending limbs (mTAL), nephron segments that are normally exposed to high and variable extracellular osmolality. Our findings are consistent with the existence of a cluster of integral membrane proteins in mTAL that may initiate or modulate osmotically relevant signaling pathways.
    Type of Medium: Online Resource
    ISSN: 0363-6143 , 1522-1563
    URL: Article
    DOI: 10.1152/ajpcell.2000.279.1.C136
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2000
    detail.hit.zdb_id: 1477334-X
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  • 5
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    Immunocytochemical and immunoelectron microscopic localization of α-, β-, and γ-ENaC in rat kidney
    American Physiological Society ; 2001
    In:  American Journal of Physiology-Renal Physiology Vol. 280, No. 6 ( 2001-06-01), p. F1093-F1106
    Details
    In: American Journal of Physiology-Renal Physiology, American Physiological Society, Vol. 280, No. 6 ( 2001-06-01), p. F1093-F1106
    Abstract: Epithelial sodium channel (ENaC) subunit (α, β, and γ) mRNA and protein have been localized to the principal cells of the connecting tubule (CNT), cortical collecting duct (CCD), and outer medullary collecting duct (OMCD) in rat kidney. However, the subcellular localization of ENaC subunits in the principal cells of these cells is undefined. The cellular and subcellular localization of ENaC subunits in rat kidney was therefore examined. Immunocytochemistry demonstrated the presence of all three subunits in principal cells of the CNT, CCD, OMCD, and IMCD. In cortex and outer medulla, confocal microscopy demonstrated a difference in the subcellular localization of subunits. α-ENaC was localized mainly in a zone in the apical domains, whereas β- and γ-ENaC were found throughout the cytoplasm. Immunoelectron microscopy confirmed the presence of ENaC subunits in both the apical plasma membrane and intracellular vesicles. In contrast to the labeling pattern seen in cortex, α-ENaC labeling in IMCD cells was distributed throughout the cytoplasm. In the urothelium covering pelvis, ureters, and bladder, immunoperoxidase and confocal microscopy revealed differences the presence of all ENaC subunits. As seen in CCD, α-ENaC was present in a narrow zone near the apical plasma membrane, whereas β- and γ-ENaC were dispersed throughout the cytoplasm. In conclusion, all three subunits of ENaC are expressed throughout the collecting duct (CD), including the IMCD as well as in the urothelium. The intracellular vesicular pool in CD principal cells suggests ENaC trafficking as a potential mechanism for the regulation of Na + reabsorption.
    Type of Medium: Online Resource
    ISSN: 1931-857X , 1522-1466
    URL: Article
    DOI: 10.1152/ajprenal.2001.280.6.F1093
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2001
    detail.hit.zdb_id: 1477287-5
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  • 6
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    Growth hormone-induced insulin resistance is associated with increased intramyocellular triglyceride content but unaltered VLDL-triglyceride kinetics
    American Physiological Society ; 2007
    In:  American Journal of Physiology-Endocrinology and Metabolism Vol. 292, No. 3 ( 2007-03), p. E920-E927
    Details
    In: American Journal of Physiology-Endocrinology and Metabolism, American Physiological Society, Vol. 292, No. 3 ( 2007-03), p. E920-E927
    Abstract: The ability of growth hormone (GH) to stimulate lipolysis and cause insulin resistance in skeletal muscle may be causally linked, but the mechanisms remain obscure. We investigated the impact of GH on the turnover of FFA and VLDL-TG, intramuscular triglyceride content (IMTG), and insulin sensitivity (euglycemic clamp) in nine healthy men in a randomized double-blind placebo-controlled crossover study after 8 days treatment with (A) Placebo + Placebo, (B) GH (2 mg daily) + Placebo, and (C) GH (2 mg daily) + Acipimox (250 mg × 3 daily). In the basal state, GH (B) increased FFA levels ( P 〈 0.05), palmitate turnover ( P 〈 0.05), and lipid oxidation ( P = 0.05), but VLDL-TG kinetics were unaffected. Administration of acipimox (C) suppressed basal lipolysis but did not influence VLDL-TG kinetics. In the basal state, IMTG content increased after GH (B; P = 0.03). Insulin resistance was induced by GH irrespective of concomitant acipimox ( P 〈 0.001). The turnover of FFA and VLDL-TG was suppressed by hyperinsulinemia during placebo and GH, whereas coadministration of acipimox induced a rebound increase FFA turnover and VLDL-TG clearance. We conclude that these results show that GH-induced insulin resistance is associated with increased IMTG and unaltered VLDL-TG kinetics; we hypothesize that fat oxidation in muscle tissue is an important primary effect of GH and that circulating FFA rather than VLDL-TG constitute the major source for this process; and the role of IMTG in the development of GH-induced insulin resistance merits future research.
    Type of Medium: Online Resource
    ISSN: 0193-1849 , 1522-1555
    URL: Article
    DOI: 10.1152/ajpendo.00374.2006
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2007
    detail.hit.zdb_id: 1477331-4
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  • 7
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    Increased renal adrenomedullin expression in rats with ureteral obstruction
    American Physiological Society ; 2009
    In:  American Journal of Physiology-Regulatory, Integrative and Comparative Physiology Vol. 296, No. 1 ( 2009-01), p. R185-R192
    Details
    In: American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, American Physiological Society, Vol. 296, No. 1 ( 2009-01), p. R185-R192
    Abstract: Ureteral obstruction is characterized by decreased renal blood flow that is associated with hypoxia within the kidney. Adrenomedullin (AM) is a peptide hormone with tissue-protective capacity that is stimulated through hypoxia. We tested the hypothesis that ureteral obstruction stimulates expression of AM and hypoxia-inducible factor-1 (HIF-1α) in kidneys. Rats were exposed to bilateral ureteral obstruction (BUO) for 2, 6, 12, and 24 h or sham operation and compared with unilateral obstruction (UUO). AM mRNA expression was measured by quantitative PCR in cortex and outer medulla (C+OM) and inner medulla (IM). AM and HIF-1α protein abundance and localization were determined in rats subjected to 24-h BUO. AM mRNA expression in C+OM increased significantly after 12-h BUO and further increased after 24 h. In IM, AM mRNA expression increased significantly in response to BUO for 6 h and further increased after 24 h. AM peptide abundance was enhanced in C+OM and IM after 24-h BUO. Immunohistochemical labeling of kidneys showed a wider distribution and more intense AM signal in 24-h BUO compared with Sham. In UUO rats, AM mRNA expression increased significantly in IM of the obstructed kidney compared with nonobstructed and Sham kidney whereas AM peptide increased in IM compared with Sham. HIF-1α protein abundance increased significantly in IM after 24-h BUO compared with Sham and HIF-1α immunoreactive protein colocalized with AM. In summary, AM and HIF-1α expression increases in response to ureteral obstruction in agreement with expected oxygen gradients. Hypoxia acting through HIF-1α accumulation may be an important pathway for the renal response to ureteral obstruction.
    Type of Medium: Online Resource
    ISSN: 0363-6119 , 1522-1490
    URL: Article
    DOI: 10.1152/ajpregu.00170.2008
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2009
    detail.hit.zdb_id: 1477297-8
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  • 8
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    Urinary tract obstruction induces transient accumulation of COX-2-derived prostanoids in kidney tissue
    American Physiological Society ; 2010
    In:  American Journal of Physiology-Regulatory, Integrative and Comparative Physiology Vol. 298, No. 4 ( 2010-04), p. R1017-R1025
    Details
    In: American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, American Physiological Society, Vol. 298, No. 4 ( 2010-04), p. R1017-R1025
    Abstract: Inhibitors of cyclooxygenase (COX)-2 prevent suppression of aquaporin-2 and reduce polyuria in the acute phase after release of bilateral ureteral obstruction (BUO). We hypothesized that BUO leads to COX-2-mediated local accumulation of prostanoids in inner medulla (IM) tissue. To test this, rats were subjected to BUO and treated with selective COX-1 or COX-2 inhibitors. Tissue was examined at 2, 6, 12, and 24 h after BUO. COX-2 protein abundance increased in IM 12 and 24 h after onset of BUO but did not change in cortex. COX-1 did not change at any time points in any region. A full profile of all five primary prostanoids was obtained by mass spectrometric determination of PGE 2 , PGF 2α , 6-keto-PGF 1α , PGD 2 , and thromboxane (Tx) B 2 concentrations in kidney cortex/outer medulla and IM fractions. IM concentration of PGE 2 , 6-keto-PGF 1α , and PGF 2α was increased at 6 h BUO, and PGE 2 and PGF 2α increased further at 12 h BUO. TxB 2 increased after 12 h BUO. 6-keto-PGF 1α remained significantly increased after 24 h BUO. The COX-2 inhibitor parecoxib lowered IM PGE 2, TxB 2 , 6-keto-PGF 1α , and PGF 2α below vehicle-treated BUO and sham rats at 6, 12 and, 24 h BUO. The COX-1 inhibitor SC-560 lowered PGE 2 , PGF 2α , and PGD 2 in IM compared with untreated 12 h BUO, but levels remained significantly above sham. In cortex tissue, PGE 2 and 6-keto-PGF 1α concentrations were elevated at 6 h only. In conclusion, COX-2 activity contributes to the transient increase in prostacyclin metabolite 6-keto-PGF 1α and TxB 2 concentration in the kidney IM, and COX-2 is the predominant isoform that is responsible for accumulation of PGE 2 and PGF 2α with minor, but significant, contributions from COX-1. PGD 2 synthesis is mediated exclusively by COX-1. In BUO, therapeutic interventions aimed at the COX-prostanoid pathway should target primarily COX-2.
    Type of Medium: Online Resource
    ISSN: 0363-6119 , 1522-1490
    URL: Article
    DOI: 10.1152/ajpregu.00336.2009
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2010
    detail.hit.zdb_id: 1477297-8
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  • 9
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    The α 1G -subunit of a voltage-dependent Ca 2+ channel is localized in rat distal nephron and collecting duct
    American Physiological Society ; 2000
    In:  American Journal of Physiology-Renal Physiology Vol. 279, No. 6 ( 2000-12-01), p. F997-F1005
    Details
    In: American Journal of Physiology-Renal Physiology, American Physiological Society, Vol. 279, No. 6 ( 2000-12-01), p. F997-F1005
    Abstract: The molecular type and localization of calcium channels along the nephron are not well understood. In the present study, we assessed the distribution of the recently identified α 1G -subunit encoding a voltage-dependent calcium channel with T-type characteristics. Using a RNase protection assay, α 1G -mRNA levels in kidney regions were determined as inner medulla ≫ outer medulla ≅ cortex. RT-PCR analysis of microdissected rat nephron segments revealed α 1G expression in the distal convoluted tubule (DCT), in the connecting tubule and cortical collecting duct (CT+CCD), and inner medullary collecting duct (IMCD). α 1G mRNA was expressed in the IMCD cell line mIMCD-3. Single- and double-labeling immunohistochemistry and confocal laser microscopy on semithin paraffin sections of rat kidneys by using an anti-α 1G antibody demonstrated a distinct labeling at the apical plasma membrane domains of DCT cells, CT principal cells, and IMCD principal cells.
    Type of Medium: Online Resource
    ISSN: 1931-857X , 1522-1466
    URL: Article
    DOI: 10.1152/ajprenal.2000.279.6.F997
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2000
    detail.hit.zdb_id: 1477287-5
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  • 10
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    Aquaporin-1 and endothelial nitric oxide synthase expression in capillary endothelia of human peritoneum
    American Physiological Society ; 1998
    In:  American Journal of Physiology-Heart and Circulatory Physiology Vol. 275, No. 1 ( 1998-07-01), p. H234-H242
    Details
    In: American Journal of Physiology-Heart and Circulatory Physiology, American Physiological Society, Vol. 275, No. 1 ( 1998-07-01), p. H234-H242
    Abstract: Water transport during peritoneal dialysis (PD) requires ultrasmall pores in the capillary endothelium of the peritoneum and is impaired in the case of peritoneal inflammation. The water channel aquaporin (AQP)-1 has been proposed to be the ultrasmall pore in animal models. To substantiate the role of AQP-1 in the human peritoneum, we investigated the expression of AQP-1, AQP-2, and endothelial nitric oxide synthase (eNOS) in 19 peritoneal samples from normal subjects ( n = 5), uremic patients treated by hemodialysis ( n = 7) or PD ( n = 4), and nonuremic patients ( n = 3), using Western blotting and immunostaining. AQP-1 is very specifically located in capillary and venule endothelium but not in small-size arteries. In contrast, eNOS is located in all types of endothelia. Immunoblot for AQP-1 in human peritoneum reveals a 28-kDa band (unglycosylated AQP-1) and diffuse bands of 35–50 kDa (glycosylated AQP-1). Although AQP-1 expression is remarkably stable in all samples whatever their origin, eNOS (135 kDa) is upregulated in the three patients with ascites and/or peritonitis (1 PD and 2 nonuremic patients). AQP-2, regulated by vasopressin, is not expressed at the protein level in human peritoneum. This study 1) supports AQP-1 as the molecular counterpart of the ultrasmall pore in the human peritoneum and 2) demonstrates that AQP-1 and eNOS are regulated independently of each other in clinical conditions characterized by peritoneal inflammation.
    Type of Medium: Online Resource
    ISSN: 0363-6135 , 1522-1539
    URL: Article
    DOI: 10.1152/ajpheart.1998.275.1.H234
    RVK:
    WA 15000
    Language: English
    Publisher: American Physiological Society
    Publication Date: 1998
    detail.hit.zdb_id: 1477308-9
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