scholarly journals Trafficking of Na-K-ATPase and dopamine receptor molecules induced by changes in intracellular sodium concentration of renal epithelial cells

2008 ◽  
Vol 295 (4) ◽  
pp. F1117-F1125 ◽  
Author(s):  
Angel R. Cinelli ◽  
Riad Efendiev ◽  
Carlos H. Pedemonte
Keyword(s):  
Plasma Membrane ◽  
Epithelial Cells ◽  
Atpase Activity ◽  
Proximal Tubule ◽  
Dopamine Receptors ◽  
Sodium Concentration ◽  
Intracellular Sodium ◽  
Proximal Tubules ◽  
Sodium Reabsorption ◽  
Intracellular Sodium Concentration

Most of the transepithelial transport of sodium in proximal tubules occurs through the coordinated action of the apical sodium/proton exchanger and the basolateral Na-K-ATPase. Hormones that regulate proximal tubule sodium excretion regulate the activities of these proteins. We have previously demonstrated that the level of intracellular sodium concentration modulates the regulation of Na-K-ATPase activity by angiotensin II and dopamine. An increase of a few millimolars in intracellular sodium concentration leads to increased Na-K-ATPase activity without a statistically significant increase in the number of plasma membrane Na-K-ATPase molecules, as determined by cell surface protein biotinylation. Using total internal reflection fluorescence, we detected an increased number of Na-K-ATPase molecules in cytosolic compartments adjacent to the plasma membrane, suggesting that the increased intracellular sodium concentration induces a movement of Na-K-ATPase molecules toward the plasma membrane. While intracellular compartments containing Na-K-ATPase molecules are very close to the plasma membrane, compartments containing type 1 dopamine receptors (D1Rs) are distributed in different parts of the cell cytosol. Fluorescence determinations indicate that an increased intracellular sodium concentration induces the increased colocalization of dopamine receptors with Na-K-ATPase molecules in the region of the plasma membrane. We propose that under in vivo conditions, in response to a sodium load in the lumen of proximal tubules, an increased level of intracellular sodium in epithelial cells is an early event that triggers the cellular response that leads to dopamine inhibition of proximal tubule sodium reabsorption.

scholarly journals Agonist-dependent Regulation of Renal Na+,K+-ATPase Activity Is Modulated by Intracellular Sodium Concentration

2002 ◽  
Vol 277 (13) ◽  
pp. 11489-11496 ◽  
Author(s):  
Riad Efendiev ◽  
Alejandro M. Bertorello ◽  
Ruben Zandomeni ◽  
Angel R. Cinelli ◽  
Carlos H. Pedemonte
Keyword(s):  
Atpase Activity ◽  
Sodium Concentration ◽  
Intracellular Sodium ◽  
Intracellular Sodium Concentration

Beta 2-adrenergic function in cultured rat proximal tubule epithelial cells

1996 ◽  
Vol 271 (1) ◽  
pp. F71-F77 ◽  
Author(s):  
H. Singh ◽  
S. Linas
Keyword(s):  
Epithelial Cells ◽  
Atpase Activity ◽  
Proximal Tubule ◽  
Sodium Transport ◽  
Cultured Cells ◽  
Proximal Tubules ◽  
Beta 2 ◽  
Acid Loading ◽  
Rat Proximal Tubule ◽  
Stimulation Of

We conducted studies to determine whether functional beta 2-adrenoceptors are present in cultured rat proximal tubule epithelial cells. To determine whether cultured cells maintain polarity with respect to sodium transport, cells were acid loaded. Acid loading resulted in stimulation of sodium transport. Exposure of acid-loaded cells to alkaline extracellular pH further enhanced sodium transport (22Na flux at pH 7.50 was 68.1 +/- 44% above pH 7.00, P < 0.05). Cultured proximal tubules also exhibited basolateral 86Rb uptake, 65% of which was ouabain sensitive. Thus cultured cells maintain apical Na/H antiport and basolateral Na-K-adenosinetriphosphatase (Na-K-ATPase). Metaproterenol (10(-6) M), a selective beta 2-agonist, stimulated Na-K-ATPase activity by 36 +/- 6% above control (P < 0.05). The stimulatory effect was blocked by ICI-118551, a selective beta 2-antagonist. To determine whether metaproterenol-dependent increases in Na-K-ATPase were dependent on apical sodium entry, apical entry was blocked with dimethylamiloride or maximized with monensin. Both dimethylamiloride and monensin prevented metaproterenol activation of Na-K-ATPase. Metaproterenol-mediated increases in Na-K-ATPase activity were associated with increases in sodium transport (27 +/- 10% above control, P < 0.05), which was prevented by dimethylamiloride. In contrast to isoproterenol, metaproterenol did not stimulate cAMP production. In summary, we have shown that functional beta 2-adrenoceptors are present on cultured rat proximal tubules. beta 2-Adrenoceptor activation results in increases in Na-K-ATPase and Na transport as a consequence of increased apical sodium entry.

Beta-adrenergic receptor function in rat proximal tubule epithelial cells in culture

1995 ◽  
Vol 268 (4) ◽  
pp. F553-F560 ◽  
Author(s):  
A. S. Hanson ◽  
S. L. Linas
Keyword(s):  
Epithelial Cells ◽  
Adenylate Cyclase ◽  
Proximal Tubule ◽  
Adrenergic Receptors ◽  
Proximal Tubules ◽  
Sodium Reabsorption ◽  
Scatchard Analysis ◽  
Beta Adrenergic ◽  
Alpha Adrenergic Receptors ◽  
And Function

The adrenergic system is important in regulating proximal tubule sodium reabsorption. Although alpha-adrenergic receptors have been identified in proximal tubules, the presence and function of beta-adrenergic receptors (BAR) in proximal tubules is less certain. The purpose of our study was to determine whether functional BAR are present on apical or basolateral surfaces of proximal tubule epithelial cells (PTEC) of rat kidney. We specifically focused on BAR coupling to adenylate cyclase and on differences between requirements for apical and basolateral receptor coupling to adenylate cyclase. To determine BAR expression and function, primary cultures of rat PTECs were grown on permeable supports. Scatchard analysis of 125I-labeled cyanopindolol binding revealed a single class of receptors on both apical and basolateral surfaces. Apical isoproterenol (ISO) resulted in time- and concentration-dependent increases in adenosine 3',5'-cyclic monophosphate (cAMP) that were 50% of responses after basolateral ISO. Apical BAR-cAMP coupling was mediated by B1-adrenergic receptors (B1AR), since apical cAMP responses were abrogated with apical (but not basolateral) B1 but not B2 antagonists. Apical B1AR required endocytosis prior to adenylate cyclase activation, since increases in cAMP were prevented by phenylarsine oxide or colchicine. B1AR-adenylate cyclase coupling was independent of intra- or extracellular calcium, cyclooxygenase metabolites, and protein kinase C (PKC) and dependent on Gs guanine nucleotide regulatory protein. Prolonged exposure to ISO resulted in time- and concentration-dependent homologous desensitization of cAMP responses. Desensitization was independent of receptor sequestration, PKA, or PKC. We conclude the following: B1AR are present on both apical and basolateral surfaces of rat PTECs.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals STUDY OF THE EFFECT OF HYPOTHERMIC CONSERVATION ON THE INTRACELLULAR SODIUM CONCENTRATION IN THE ENDOTHELIUM OF CORNEAL TRANSPLANTS

2018 ◽  
Vol 22 (4) ◽  
pp. 433-437
Author(s):  
G. S. Baturina ◽  
I. G. Palchikova ◽  
A. A. Konev ◽  
E. S. Smirnov ◽  
L. E. Katkova ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Plasma Membranes ◽  
Sodium Concentration ◽  
Intracellular Sodium ◽  
Sodium Balance ◽  
Human Cornea ◽  
Sodium Permeability ◽  
Custom Made ◽  
Intracellular Sodium Concentration ◽  
Cornea Endothelium

Endothelial keratoplasty has become the treatment of choice for corneal endothelial dysfunction. Advancements in the surgical treatment of corneal endothelial diseases depend on progress in graft conservation and its related advantages in assessing the suitability of grafts for transplantation. Transport of water and ions by cornea endothelium is important for the optic properties of cornea. In this work, we study the intracellular sodium concentration in cornea endothelial cells in samples of pig cornea that underwent hypothermic conservation for 1 and 10 days and endothelial cells of human cornea grafts after 10-day conservation. The concentration of intracellular sodium in preparations of endothelial cells was assayed using fluorescent dye SodiumGreen. The fluorescent images were analyzed with the custom-made computer program CytoDynamics. An increased level of intracellular sodium was shown in the endothelium after 10-day conservation in comparison with one-day conservation (pig samples). Sodium permeability of pig endothelial cell plasma membranes significantly decreased in these samples. Assessment of intracellular sodium in human cornea endothelium showed a higher level – as was in analogues pig samples of the corneal endothelium. The assay of the intracellular sodium balance concentration established in endothelial cells after hypothermic conservation in mediums L-15 and Optisol-GS showed a significant advantage of specialized me dium Optisol-GS. The balanced intracellular concentration after 10 days of hypothermic conservation was significantly lower in cells incubated at 4 °C in Optisol-GS (L-15, 128 ± 14,  n = 15; Optisol-GS, 108 ± 14, n = 11; mM, p < 0.001). Intracellular sodium concentration could be a useful parameter for assessing cornea endothelium cell viability.

scholarly journals Immunoelectron Microscopic Localization of the Electrogenic Na/HCO3 Cotransporter in Rat and Ambystoma Kidney

2000 ◽  
Vol 11 (12) ◽  
pp. 2179-2189
Author(s):  
ARVID B. MAUNSBACH ◽  
HENRIK VORUM ◽  
TAE-HWAN KWON ◽  
SØREN NIELSEN ◽  
BRIAN SIMONSEN ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Proximal Tubule ◽  
Rat Kidney ◽  
Proximal Tubules ◽  
Kidney Cortex ◽  
Apical Plasma Membrane ◽  
Rat Kidney Cortex ◽  
C Terminus ◽  
Basolateral Plasma Membrane ◽  
Intracellular Vesicles

Abstract. Immunofluorescence analysis has revealed that electrogenic Na+/HCO3- (NBC1) is expressed in the proximal tubule of rat kidney and in the proximal and distal tubules of the salamander Ambystoma tigrinum kidney. The present study was undertaken to define the detailed subcellular localization of the NBC1 in rat and Ambystoma kidney using high-resolution immunoelectron microscopy. For this purpose, two rabbit polyclonal antibodies raised against amino acids 928 to 1035 and amino acids 1021 to 1035 of the C-terminus of rat kidney (rkNBC1) were developed. The affinity-purified antibodies revealed a strong band of approximately 140 kD in immunoblots of membranes from rat kidney cortex but no signal in membranes isolated from outer and inner medulla. Deglycosylation reduced the apparent molecular weight to approximately 120 kD, corresponding to the predicted molecular weight. A similar but weaker band was also present in membranes isolated from the lateral part of Ambystoma kidney. In rat kidney, immunohistochemistry confirmed the presence of rkNBC1 in convoluted segments of the proximal tubules. In ultrathin cryosections or Lowicryl HM20 sections from rat kidney cortex, distinct immunogold labeling was associated with the basolateral plasma membrane of segments S1 and S2 of proximal tubules, whereas in S3 no labeling was observed. The labeling density was similar at the basal and lateral plasma membrane and was specifically associated with the inner surface of the membrane consistent with the internal position of the C-terminus of the transporter. In contrast, rkNBC1 was absent from the apical plasma membrane and not observed in intracellular vesicles, including those closely associated with basolateral plasma membrane. In Ambystoma kidney, a weak labeling was present in the basolateral membrane of the proximal tubule and stronger labeling was observed in the late distal segment. The results demonstrate that rkNBC1 is expressed only in segment S1 and segment S2 of rat proximal tubule as well as Ambystoma proximal and late distal tubule and that rkNBC1 is present in both basal and lateral plasma membranes and absent in intracellular vesicles of the apical plasma membrane.

Effect of renal perfusion pressure on sodium reabsorption from proximal tubules of superficial and deep nephrons

1986 ◽  
Vol 250 (3) ◽  
pp. F425-F429 ◽  
Author(s):  
J. A. Haas ◽  
J. P. Granger ◽  
F. G. Knox
Keyword(s):  
Proximal Tubule ◽  
Perfusion Pressure ◽  
Renal Perfusion ◽  
Proximal Tubules ◽  
Sodium Reabsorption ◽  
Renal Perfusion Pressure ◽  
Henle's Loop ◽  
Acute Change ◽  
Acute Changes ◽  
Superficial And Deep Nephrons

Previous studies in rats have demonstrated that superficial proximal tubule sodium reabsorption does not change in response to alterations in renal perfusion pressure (RPP). The first objective of the present study was to estimate sodium reabsorption in response to acute changes in RPP utilizing fractional lithium reabsorption (FRLi) as an index of fractional sodium reabsorption (FRNa) by the proximal tubule of the kidney as a whole. FRLi decreased in response to increases in RPP, suggesting that sodium reabsorption by the proximal tubule of some nephron population is decreased. Therefore, the second objective of the present study was to test the hypothesis that superficial and deep proximal tubules respond differently to changes in RPP by comparing proximal tubule sodium reabsorption from both nephron populations. In response to an acute change in RPP from 114 +/- 4 to 138 +/- 5 mmHg, FRNa by the proximal tubule and descending limb of Henle's loop in deep nephrons decreased from 71.3 +/- 2.3 to 55.8 +/- 5.6%, but FRNa by the superficial late proximal tubule was not changed: (44.3 +/- 4.8 to 45.1 +/- 3.9%). The urinary fractional reabsorption of sodium decreased from 96.7 +/- 0.6 to 94.5 +/- 0.5%. In summary, these studies demonstrate that increases in RPP have no effect on sodium reabsorption by the proximal tubule of superficial nephrons. In contrast, sodium delivery to the point of micropuncture in the descending limb of Henle's loop of deep nephrons was increased, suggesting inhibition of sodium reabsorption by proximal tubules of deep nephrons in response to increases in RPP.

The influence of changes in extracellular and intracellular sodium concentration on detrusor contractility

2006 ◽  
Vol 97 (5) ◽  
pp. 1083-1086 ◽  
Author(s):  
DLER BESARANI ◽  
CHANGHAO WU ◽  
CHRISTOPHER H. FRY
Keyword(s):  
Sodium Concentration ◽  
Intracellular Sodium ◽  
Detrusor Contractility ◽  
Intracellular Sodium Concentration
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