scholarly journals Aquaporin-1 water channel expression in human kidney.

1997 ◽  
Vol 8 (1) ◽  
pp. 1-14
Author(s):  
A B Maunsbach ◽  
D Marples ◽  
E Chin ◽  
G Ning ◽  
C Bondy ◽  
...  
Keyword(s):  
Proximal Tubule ◽  
Water Channel ◽  
Neck Region ◽  
Human Kidney ◽  
Proximal Tubules ◽  
Mrna Levels ◽  
Outer Medulla ◽  
Aquaporin 1 ◽  
Peritubular Capillaries

The pattern of aquaporin-1 water channel protein (AQP1) expression in the human kidney was analyzed by immunocytochemistry using semi-thin and optimized high-resolution immunoelectron microscopy based on freeze-substituted and Lowicryl HM20 embedded tissue. In addition, in situ hybridization was used to determine AQP1 mRNA distribution. Immunoblots revealed a 28-kd band and a 35- to 45-kd band corresponding to unglycosylated and glycosylated AQP1. Glomerular capillary endothelium exhibited extensive AQP1 labeling, whereas glomerular podocytes and Bowman's capsule epithelium were unlabeled. AQP1 was localized in the proximal tubule, including the neck region directly connected to the glomerulus. However, there was a marked difference in the level of expression between cross-sections of the convoluted part and the proximal straight tubules, the latter displaying the most intense labeling. AQP1 labeling continued uninterrupted from the proximal straight tubule into descending thin limbs in outer medulla. Abrupt transitions from heavily labeled to unlabeled segments of thin limbs were observed, primarily in the inner medulla. This may represent the transition from the water-permeable thin descending limb to the water-impermeable thin ascending limb. In addition, heavy labeling of fenestrated endothelium was also observed in peritubular capillaries in cortex, outer medulla, and inner medulla. Immunolabeling controls were negative. In situ hybridization documented a marked difference in AQP1 mRNA levels within the proximal tubule, with the greatest AQP1 mRNA expression in straight proximal tubules. Glomeruli also showed marked signals, and descending thin limbs exhibited extensive expression in exact concordance with the immunocytochemical results. It was concluded that: (1) AQP1 is present in all proximal tubule segments, including segment 1 and the neck region, but there is a pronounced difference in expression levels with respect to both protein and mRNA levels; (2) AQP1 labeling is observed in the endothelium of fenestrated peritubular capillaries, as well as fenestrated glomerular capillaries; (3) AQP1 labeling continues directly from proximal tubules to descending thin limbs; and (4) abrupt transitions from labeled to unlabeled thin limb epithelium are noted.

Effects of formate and oxalate on volume absorption in rat proximal tubule

1992 ◽  
Vol 263 (1) ◽  
pp. F37-F42 ◽  
Author(s):  
T. Wang ◽  
G. Giebisch ◽  
P. S. Aronson
Keyword(s):  
Proximal Tubule ◽  
Channel Blocker ◽  
Ringer Solution ◽  
Proximal Tubules ◽  
Solution Ph ◽  
Physiological Range ◽  
Volume Absorption ◽  
Peritubular Capillaries ◽  
Rat Proximal Tubule

We examined the effects of formate and oxalate on the rate of fluid absorption (Jv) in the rat proximal convoluted tubule in situ. Proximal tubules were microperfused with a high-Cl-, low-HCO3- Ringer solution (pH 6.7), and the peritubular capillaries were perfused with a standard Ringer solution (pH 7.4), simulating conditions in the late proximal tubule. Jv, a measure of transtubular NaCl absorption under these conditions, was calculated from the change in luminal [3H]inulin. Addition of formate in the physiological range (500 microM) to the luminal perfusate increased Jv by 45%; addition of 500 microM formate to both luminal and capillary perfusates increased Jv by 57%. Similarly, addition of oxalate in the physiological range (5 microM) to the luminal perfusate increased Jv by 37%; addition of 5 microM oxalate to both luminal and capillary perfusates increased Jv by 57%. The stimulatory effects of formate and oxalate perfused in the lumen and capillaries were not additive. Addition of 4,4'-diisothiocyanostilbene-2,2'-disulfonate (DIDS, 0.1 mM) to the luminal perfusate had no effect on baseline Jv measured in the absence of added formate and oxalate but completely abolished the increment in Jv induced by formate and oxalate. Addition of the Cl(-)-channel blocker diphenylamine-2-carboxylate (DPC, 0.2 mM) to the capillary perfusate had no effect on baseline Jv but completely abolished the increment in Jv induced by formate and oxalate.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Transepithelial water and urea permeabilities of isolated perfused Munich-Wistar rat inner medullary thin limbs of Henle's loop

2014 ◽  
Vol 306 (1) ◽  
pp. F123-F129 ◽  
Author(s):  
C. Michele Nawata ◽  
Kristen K. Evans ◽  
William H. Dantzler ◽  
Thomas L. Pannabecker
Keyword(s):  
Water Channel ◽  
Wistar Rat ◽  
Structural Features ◽  
Urea Transporter ◽  
Outer Medulla ◽  
Aquaporin 1 ◽  
Passive Mechanism ◽  
Short Loop ◽  
Osmotic Water ◽  
Gene Expression Levels

To better understand the role that water and urea fluxes play in the urine concentrating mechanism, we determined transepithelial osmotic water permeability ( Pf) and urea permeability ( Purea) in isolated perfused Munich-Wistar rat long-loop descending thin limbs (DTLs) and ascending thin limbs (ATLs). Thin limbs were isolated either from 0.5 to 2.5 mm below the outer medulla (upper inner medulla) or from the terminal 2.5 mm of the inner medulla. Segment types were characterized on the basis of structural features and gene expression levels of the water channel aquaporin 1, which was high in the upper DTL (DTLupper), absent in the lower DTL (DTLlower), and absent in ATLs, and the Cl-1 channel ClCK1, which was absent in DTLs and high in ATLs. DTLupper Pf was high (3,204.5 ± 450.3 μm/s), whereas DTLlower showed very little or no osmotic Pf (207.8 ± 241.3 μm/s). Munich-Wistar rat ATLs have previously been shown to exhibit no Pf. DTLupper Purea was 40.0 ± 7.3 × 10−5 cm/s and much higher in DTLlower (203.8 ± 30.3 × 10−5 cm/s), upper ATL (203.8 ± 35.7 × 10−5 cm/s), and lower ATL (265.1 ± 49.8 × 10−5 cm/s). Phloretin (0.25 mM) did not reduce DTLupper Purea, suggesting that Purea is not due to urea transporter UT-A2, which is expressed in short-loop DTLs and short portions of some inner medullary DTLs close to the outer medulla. In summary, Purea is similar in all segments having no osmotic Pf but is significantly lower in DTLupper, a segment having high osmotic Pf. These data are inconsistent with the passive mechanism as originally proposed.

scholarly journals Gene Expression Levels and Immunolocalization of Organic Ion Transporters in the Human Kidney

2002 ◽  
Vol 13 (4) ◽  
pp. 866-874
Author(s):  
Hideyuki Motohashi ◽  
Yuji Sakurai ◽  
Hideyuki Saito ◽  
Satohiro Masuda ◽  
Yumiko Urakami ◽  
...  
Keyword(s):  
Basolateral Membrane ◽  
Mrna Level ◽  
Human Kidney ◽  
Proximal Tubules ◽  
Mrna Levels ◽  
Ion Transporters ◽  
Ion Transporter ◽  
Transporter Family ◽  
Immunohistochemical Analyses ◽  
Gene Expression Levels

ABSTRACT. Renal excretion of organic anions and cations is mediated by the organic ion transporter family (SLC22A). In this study, the mRNA levels of the organic ion transporters were quantified by real-time PCR in normal parts of renal tissues from seven nephrectomized patients with renal cell carcinoma, and the distributions and localization of human (h)OAT1, hOAT3, and hOCT2 proteins were investigated by immunohistochemical analyses in the human kidney. The expression level of hOAT3 mRNA was the highest among the organic ion transporter family, followed by that of hOAT1 mRNA. The hOCT2 mRNA level was the highest in the human OCT family, and the level of hOCTN2 mRNA was higher than that of hOCTN1. hOCT1 mRNA showed the lowest level of expression in organic ion transporter family. hOAT1, hOAT3, and hOCT2 proteins were detected in crude membranes from the kidney of all patients by Western blot analyses, whereas hOCT1 protein could not be detected. Immunohistochemical analyses showed that both hOAT1 and hOAT3 were localized to the basolateral membrane of the proximal tubules in the cortex, and hOCT2 was localized to the basolateral membrane of the proximal tubules in both the cortex and medullary ray. Immunohistochemical analyses of serial sections indicated that hOAT1, hOAT3, and hOCT2 were coexpressed in a portion of the proximal tubules. These results suggest that hOAT1, hOAT3, and hOCT2 play predominant roles in the transport of organic ions across the basolateral membrane of human proximal tubules.

Mechanisms of stimulation of proximal tubule chloride transport by formate and oxalate

1996 ◽  
Vol 271 (2) ◽  
pp. F446-F450 ◽  
Author(s):  
T. Wang ◽  
A. L. Egbert ◽  
T. Abbiati ◽  
P. S. Aronson ◽  
G. Giebisch
Keyword(s):  
Proximal Tubule ◽  
Chloride Transport ◽  
Rat Kidney ◽  
Exchange Process ◽  
Exchange Inhibitor ◽  
Volume Absorption ◽  
Peritubular Capillaries ◽  
Rat Proximal Tubule ◽  
Stimulation Of

We have previously demonstrated that formate and oxalate stimulate volume absorption in the rat proximal tubule, consistent with Cl-/formate and Cl-/oxalate exchange process across the apical membrane. To sustain Cl- absorption by these processes requires mechanisms for recycling formate and oxalate from lumen to cell. The aims of the present study were to characterize these mechanisms of formate and oxalate recycling. Proximal tubules and peritubular capillaries were simultaneously microperfused in the rat kidney in situ. Serum formate concentration was determined to be 56.5 +/- 7.7 microM. Addition of 5, 50, and 500 microM formate to both luminal and capillary perfusates significantly increased net Cl- absorption (Jcl) by 26, 26, and 46%, respectively. Jcl was stimulated 38% by 1 microM oxalate added to the perfusates. Removal of sulfate completely prevented the stimulation of Jcl by 1 microM oxalate but had no effect on the stimulation of Jcl by formate. Luminal addition of the Na+/H+ exchange inhibitor ethylisopropylamiloride completely blocked the stimulation of Jcl by 50 microM formate but had no effect on stimulation by oxalate. We conclude that physiological concentrations of formate and oxalate markedly stimulate Cl- and fluid absorption in the rat proximal convoluted tubule. Whereas formate recycling most likely involves Na+/H+ exchange in parallel with H(+)-coupled formate entry, oxalate recycling involves sodium-sulfate cotransport in parallel with sulfate/oxalate exchange.

Localization of angiotensin II type 1 receptor subtype mRNA in rat kidney

1995 ◽  
Vol 268 (2) ◽  
pp. F220-F226 ◽  
Author(s):  
D. P. Healy ◽  
M. Q. Ye ◽  
M. Troyanovskaya
Keyword(s):  
In Situ Hybridization ◽  
Rat Kidney ◽  
At1 Receptor ◽  
Receptor Subtypes ◽  
Mrna Levels ◽  
Ang Ii ◽  
Outer Medulla ◽  
Vasa Recta

The physiological effects of angiotensin II (ANG II) on the kidney are mediated primarily by the ANG II type 1 (AT1) receptor. Two highly similar AT1 receptor subtypes have been identified in the rat by molecular cloning techniques, namely AT1A and AT1B. The intrarenal localization of the AT1A and AT1B receptor subtypes has not been studied by hybridization methods with subtype-specific receptor probes. Using radiolabeled probes from the 3' noncoding region of the AT1A and AT1B cDNAs, we localized AT1 mRNA in rat kidney by in situ hybridization. Specificity of the 3' noncoding region probes was tested by Northern blot and solution hybridization methods. AT1A mRNA levels were highest in the liver, kidney, and adrenal. In contrast, AT1B mRNA levels were highest in the adrenal and pituitary and low in kidney. Autoradiographic localization of 125I-[Sar1,Ile8]ANG II binding indicated that the highest levels of AT1 receptors were found in glomeruli and vascular elements. In situ hybridization with a nonselective AT1 receptor riboprobe indicated that the highest levels of AT1 mRNA were in the outer medullary vasa recta and cortical glomeruli with additional diffuse labeling of the cortex and outer medulla, consistent with labeling of tubular elements. In contrast, in situ hybridization with the AT1 subtype selective probes revealed that AT1A receptor mRNA was primarily localized to the vasa recta and diffusely to the outer stripe of the outer medulla and the renal cortex.(ABSTRACT TRUNCATED AT 250 WORDS)

Single proximal tubules of Necturus kidney. VIII: Na and K determinations by glass electrodes

1963 ◽  
Vol 204 (5) ◽  
pp. 743-748 ◽  
Author(s):  
Raja N. Khuri ◽  
David A. Goldstein ◽  
David L. Maude ◽  
Charles Edmonds ◽  
A. K. Solomon
Keyword(s):  
Proximal Tubule ◽  
Distal Portion ◽  
Proximal Tubules ◽  
Living Animal ◽  
Flame Photometer ◽  
Proximal Tubular ◽  
Glass Electrodes ◽  
K Concentration

Cation-sensitive glass electrodes have been used to measure Na and K concentrations in Necturus serum and in glomerular and proximal tubular fluid from Necturus kidney. It has been found that the ratio [Na]glomerulus/[Na]serum is 1.00 ± 0.02 and the ratio [Na]tubule/[Na]glomerulus is 0.99 ± 0.01 thus confirming previous measurements with the flame photometer which indicated that tubular Na concentration did not change as fluid moved along the proximal tubule in Necturus kidney. These results were also confirmed with cation electrodes placed in situ in the living animal. The K concentration in fluid collected from the most distal portion of the proximal tubule was found to be 1.8 ± 0.1 times more concentrated than that in the glomerulus, in agreement with a ratio of 1.6 ± 0.1 previously obtained on the basis of flame photometer measurements by Oken and Solomon.

Filled pore approximation: a theoretical framework for solute-solvent coupling in narrow water channels

1996 ◽  
Vol 270 (4) ◽  
pp. C1246-C1254 ◽  
Author(s):  
D. J. Welling ◽  
P. A. Welling ◽  
L. W. Welling
Keyword(s):  
Proximal Tubule ◽  
Basolateral Membrane ◽  
Water Channel ◽  
Water Volume ◽  
Aquaporin 1 ◽  
Single File ◽  
Frictional Interaction ◽  
Frictional Coefficients ◽  
Limiting Condition ◽  
Water And Solute Transport

A phenomenological model is presented of water and solute transport that is applicable to water pores with radii less than approximately 2 A. This includes such examples as gramicidin A, the proximal tubule basolateral membrane, and the aquaporin 1 (CHIP28) water channel. The model differs from the conventional single-file model by allowing for a variation of unoccupied volume within the pores. It is shown that the accessible or free portion of the unoccupied volume can be related to the mechanical frictional coefficients and thereby to the filtration and diffusive permeabilities by the filled pore approximation. In general, the smallness of the unoccupied volume represents the compactness of the molecules within the pore and is indicative of the single-file character of the motion of water and solute moving together. When that volume is equal to a single water volume, the results are identical to the conventional single-file model. An important result is that, despite very low diffusive permeabilities, the reflection coefficient of a solute can remain at approximately 0.5 if its frictional interaction with the channel walls is comparable with its frictional interaction with neighboring water molecules. This is consistent with values previously reported for NaCl in cell membranes of proximal tubule. The model predicts a minimum effective pore radius for a water channel of 1.78 A and corresponds to a maximum filtration-to-diffusion permeability ratio that is proportional to the length of the effective pore or channel. This limiting condition corresponds to a water channel completely filled by water and may be applicable to the aquaporin 1 water channel.

Potassium deprivation upregulates expression of renal basolateral Na+-HCO3 −cotransporter (NBC-1)

2000 ◽  
Vol 279 (3) ◽  
pp. F532-F543 ◽  
Author(s):  
Hassane Amlal ◽  
Khalid Habo ◽  
Manoocher Soleimani
Keyword(s):  
Proximal Tubule ◽  
Collecting Duct ◽  
Thick Ascending Limb ◽  
Mrna Levels ◽  
Time Intervals ◽  
Outer Medulla ◽  
Medullary Thick Ascending Limb ◽  
Medullary Collecting Duct ◽  
Potassium Deprivation ◽  
Expression And Activity

The purpose of the present experiments was to examine the effect of potassium deprivation on the expression of the renal basolateral Na+-HCO3 − cotransporter (NBC-1). Rats were placed on a K+-free diet for various time intervals and examined. NBC-1 mRNA levels increased by about threefold in the cortex ( P < 0.04) at 72 h of K+ deprivation and remained elevated at 21 days. NBC activity increased by ∼110% in proximal tubule suspensions, with the activity increasing from 0.091 in control to 0.205 pH/min in the K+-deprived group ( P < 0.005). The inner stripe of outer medulla and cells of medullary thick ascending limb of Henle (mTAL) showed induction of NBC-1 mRNA and activity in K+-deprived rats, with the activity in mTAL increasing from 0.010 in control to 0.133 pH/min in the K+-deprived group ( P < 0.004). K+ deprivation also increased NBC-1 mRNA levels in the renal papilla ( P < 0.02). We conclude that 1) K+ deprivation increases NBC-1 expression and activity in proximal tubule and 2) K+deprivation causes induction of NBC-1 expression and activity in mTAL tubule and inner medulla. We propose that NBC-1 likely mediates enhanced HCO3 − reabsorption in proximal tubule, mTAL, and inner medullary collecting duct in K+ deprivation and contributes to the maintenance of metabolic alkalosis in this condition.

Presence and distribution of endothelin-1 gene expression in human kidney

1994 ◽  
Vol 267 (4) ◽  
pp. F679-F687 ◽  
Author(s):  
C. Pupilli ◽  
M. Brunori ◽  
N. Misciglia ◽  
C. Selli ◽  
L. Ianni ◽  
...  
Keyword(s):  
Gene Expression ◽  
Endothelial Cells ◽  
In Situ Hybridization ◽  
Renal Cortex ◽  
Cdna Probe ◽  
Renal Medulla ◽  
Human Kidney ◽  
Renal Tumors ◽  
Mrna Levels

To investigate the presence and the distribution of preproendothelin-1 (prepro-ET-1) mRNA in human kidney, eight human kidneys obtained at surgery from patients affected by localized renal tumors were studied. Northern blot analysis using a human prepro-ET-1 cDNA probe labeled with 32P showed the presence of a single band of approximately 2.3 kb that was present both in the renal cortex and medulla of all the kidneys studied. Densitometric analysis of hybridization signals demonstrated that prepro-ET-1 mRNA levels in the renal medulla were 2.2-fold higher than those in the renal cortex. The distribution of prepro-ET-1 mRNA in human kidney was investigated by in situ hybridization using a human prepro-ET-1 RNA probe labeled with 35S. The greatest density of prepro-ET-1 mRNA was observed in the renal medulla, where hybridization signal was demonstrated in vasa recta bundles and capillaries and in collecting ducts. By combining in situ hybridization with immunohistochemical detection of von Willebrand factor, we demonstrated that 93 +/- 2.5% of nontubular medullary cells containing prepro-ET-1 mRNA were endothelial cells. In the cortex, prepro-ET-1 mRNA was localized in the endothelial layer of arcuate and interlobular arteries and veins and in the endothelial cells of afferent arterioles. The results of the present study demonstrate that ET-1 gene expression is present in vascular and tubular structures of the human kidney. It is possible that ET-1 synthesized locally in the human kidney represents a local system affecting renal hemodynamics and functions through paracrine and/or autocrine actions on different renal structures.

Sign in / Sign up

Export Citation Format

Share Document