rBSC1 is differentially upregulated in different pathological conditions.

rBSC1 is up-regulated even in rats with small to moderate myocardial infarctions, which may enhance the sodium transport in the TAL in this pathophysiologic condition.

Background: Stimulation of arginine vasopressin results in an immediate redistribution of water channels (aquaporin 2; AQP2) in the apical membrane of the collecting ducts, leading to water reabsorption. Water restriction for ≧24 h increases AQP2 proteins in the whole collecting duct which is highest in the inner medulla of the kidney, indicating that dehydration enhances synthesis of this protein. Although increased expression of AQP2 mRNA under this condition has been reported, the increased ratio of mRNA expression in the three regions of the kidney, cortex, outer medulla, and inner medulla, during the dehydration is still unclear. Methods: We investigated the AQP2 transcripts using male Sprague-Dawley rats deprived of water for 24 h. Mimic cDNA for competitive polymerase chain reaction (PCR) was constructed by deleting 180 bp at the middle of a 780-bp partial PCR product for rat AQP2 cDNA. In situ hybridization of the kidney and Northern blotting of inner medulla were performed using a 60-bp oligo-cDNA probe which identified rat AQP2 transcripts in the collecting duct. Results: Dehydration resulted in a significant increase in plasma osmolality and arginine vasopressin concentration and urinary osmolality. Competitive PCR demonstrated that dehydration increased AQP2 transcripts in all parts of the kidney, but was highest in the inner medulla. Northern blotting confirmed the high increased rate of AQP2 transcription in the inner medulla. In situ hybridization showed markedly intensified signals in the inner medulla of dehydrated rats. Conclusions: Our data indicate that dehydration increases the abundance of AQP2 transcripts which may be closely associated with enhancement in AQP2 protein synthesis reported previously. This topographically variable increase in transcription is considered to be one of the mechanisms involved in long-term regulation of water permeability in the collecting duct.

Background: The type IV collagen is a complex of trimetric molecule composed of six genetically distinct polypeptide chains; α1–6(IV). Since α3(IV) distribute specifically in the glomerular basement membrane (GBM) of glomerular capillary, we tried to develop the detection methods for the transcripts of α3(IV) in glomerular epithelial cells (GEC) which produce most of the components for GBM. Then, using these molecular techniques, the influence of elastase, one of the proteases released from activated polymorphonuclear leukocytes at the site of inflammation, on GEC was determined as manifested by expressional alteration of α3(IV) mRNA. Methods: DIG-labeled oligo-DNA probe designating non-collagenous region of α3(IV) was used for in situ hybridization. Semiquantitative measurement of α3(IV) in the renal cortex was performed by PCR reactions, each reaction being normalized by that for GAPDH. Then, the femoral artery of each of 18 Sprague-Dawley rats was catheterized and the left kidney was perfused with saline alone (0.5 ml) or saline containing 100 µg/ml elastase. After collection of urine for 24 h, the left kidney was harvested for analysis of mRNA (4 for in situ hybridization and 5 kidneys for PCR analysis). Results: Antisense cDNA probe and PCR reaction well identified α3(IV) mRNA in the cytoplasm of GEC and in the renal cortex, respectively. Urinary protein excreted by rats with elastase perfusion was 47.2 ± 3.8 mg/24 h but this was only 13.9 ± 1.1 mg/24 h in control rats (mean ± SEM, p < 0.05). In situ hybridization demonstrated that expression of α3(IV) mRNA in GEC was focally or diffusely reduced in the glomeruli of rats with elastase perfusion, whereas the transcripts were well stained in GEC of controls. PCR analysis showed about 25% decrease in transcripts of α3(IV) in the renal cortex of rats with elastase perfusion compared to those of control rats. Conclusions: α3(IV) mRNA was identified specifically in the GEC in the glomeruli. Co-incidence of proteinuria and reduced α3(IV) expression by elastase suggests adverse effects of elastase on GEC and close association between proteinuria and GEC injury.

Although ischemia-reperfusion of mouse kidney is known to cause severe renal failure due to tubular cell death, the exact cellular mechanism responsible for this phenomenon is not clear. To investigate the spatial and temporal development of renal cell death and the role of Fas/APO-1/CD95 (Fas) in this process, the left renal vessels were occluded in a group of mice for 30, 60, or 120 min followed by reperfusion for 24 h (n = 4 for each group). Analysis of the isolated DNA in agarose-gel electrophoresis revealed a typical ladder pattern of bands consisting of multiples of 180 to 200 bp, considered the hallmark of apoptosis. The intensity of the bands increased proportionately with the duration of ischemia. Histochemical analysis using terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling showed the presence of nuclei with DNA double-strand breaks specifically in distal renal tubules of the outer medulla. The presence of apoptosis was also confirmed by electron microscopy. Analysis of total RNA by Northern blotting revealed one appropriate-sized band for Fas mRNA in the normal kidney, which intensified in the ischemia-reperfused kidney. Moreover, nonradioactive in situ hybridization revealed that distal renal tubular epithelial cells were positive for Fas mRNA in the outer medulla. Fas antigen was also localized to the renal tubular epithelial cells of the outer medulla by immunohistochemistry. The number of apoptotic cells in the ischemia-reperfusion kidney of the lpr/lpr mouse was low. These findings strongly indicate that ischemia-reperfusion of the kidney induces apoptosis of a specific area of tubular epithelial cells in the outer medulla through the Fas system.