Ouabain modulation of endothelial calcium signaling in descending vasa recta

Pittner, J.; Rhinehart, Kristie; Pallone, Thomas L.

doi:10.1152/ajprenal.00326.2005

Cited by 18 publications

(29 citation statements)

References 54 publications

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“…2-APB is frequently used to inhibit IP 3 receptors but is known to have other effects, particularly to block store-operated cation channels. We previously showed that 2-APB suppresses DVR endothelial [Ca 2ϩ ] CYT responses to ouabain (38). In this study, however, it did not affect STIC oscillations.…”

Section: Discussioncontrasting

confidence: 64%

“…That inhibition has been hypothesized to elevate subplasmalemmal Na ϩ and Ca 2ϩ concentrations through reduction of NCX activity, resulting in an increase in Ca 2ϩ content of ER/SR stores and bulk cytoplasm (4). Functional studies showed that this favors an increase in microvessel contractility and a rise in the Ca 2ϩ released by agonists (3,38,45). Given the dependence of STICs on Ca 2ϩ store release, we tested whether ouabain would affect their occurrence in DVR pericytes.…”

Section: Discussionmentioning

confidence: 99%

“…8). Ouabain has been hypothesized to increase the load of Ca 2ϩ within internal stores and enhance the release of Ca 2ϩ by agonists (2,3,38). Based on those considerations, we tested the hypothesis that ouabain would increase the current carried by STICs.…”

Section: Ion Movements Underlying Ang Ii-induced Stic Oscillationsmentioning

confidence: 99%

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Membrane current oscillations in descending vasa recta pericytes

Zhang

Cao²,

Zhang³

et al. 2008

American Journal of Physiology-Renal Physiology

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We investigated the origin of spontaneous transient inward current (STIC) oscillations in descending vasa recta (DVR) pericytes. In cells clamped at Ϫ80 mV, angiotensin II (ANG II; 10 nmol/l) induced oscillations with mean amplitude and frequency of Ϫ65.5 pA and 1. METHODS Isolation of DVR.Investigations involving animal use were performed according to protocols approved by the Institutional Animal Care and Use Committee of the University of Maryland. Kidneys were harvested from Sprague-Dawley rats (100 -150 g; Harlan) that had been anesthetized by an intraperitoneal injection of ketamine/ xylazine (80 mg/kg; 10 mg/kg). Tissue slices were stored at 4°C in a physiological saline solution (PSS; in mM: 155 NaCl, 5 KCl, 1 MgCl 2, 1 CaCl2, 10 HEPES, and 10 glucose, pH 7.4). Small wedges of renal medulla were dissected and transferred to Blendzyme 1 (Roche) at 0.27 mg/ml in high-glucose DMEM media (Invitrogen), incubated at 37°C for 45 min whereupon they were transferred to PSS and stored at 4°C. At intervals, DVR were isolated from the enzymedigested renal tissue and transferred to a perfusion chamber for patch-clamp recording.Whole cell patch-clamp recording. Patch pipettes were made from borosilicate glass capillaries (PG52151-4, World Precision Instruments, Sarasota, FL), using a two-stage vertical pipette puller (Narshige PP-830) and heat polished. For whole cell patch-clamp recording, the pipette solution was (in mM) 120 Kaspartate, 20 KCl, 10 NaCl, 10 HEPES, pH 7.2, with or without nystatin (100 g/ml with 0.1% DMSO) in ultrapure water. Measurements were obtained as previously described (35). Briefly, most membrane currents were measured using a CV201AU headstage and Axopatch 200 amplifier (Axon Instruments, Foster City, CA) at 10 Hz using 8-to 10-M⍀ pipettes and nystatin patches. In experiments where simultaneous recording of [Ca 2ϩ ]CYT variation and whole cell current was performed, the ruptured patch method was substituted for nystatin so that fluo-4 could diffuse into the pericyte cytoplasm.Fluorescent recording of [Ca 2ϩ ]CYT. To record [Ca 2ϩ ]CYT variations of DVR pericytes, the Ca 2ϩ -sensitive fluorescent probe, fluo-4 (Molecular Probes), was either included in the electrode buffer as the pentapotassium salt (50 M, patch-clamp recordings) or loaded into isolated DVR by incubation with the AM ester (10 mol/l, 20 min, 37°C, confocal microscopy). During patch-clamp experiments, the probe was excited at 485 nm (DeltaRam, PTI) and emissions were captured at 530 nm (B-2E/C filter cube, Nikon) using a ϫ40 CF fluor oil immersion objective, 1.3 numerical aperture. The image of the patched fluorescent pericyte was directed to a D104B photon counting photomultiplier detection assembly (PTI) set to operate in analog mode. In other experiments, to simultaneously visualize [Ca 2ϩ ]CYT transients in pericytes and endothelia and to test for their occurrence in the absence of voltage clamp, isolated, fluo-4-loaded DVR adherent to the bottom of a recording chamber were visualized by laserscanning confocal micro...

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Section: Discussioncontrasting

confidence: 64%

Section: Discussionmentioning

confidence: 99%

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Membrane current oscillations in descending vasa recta pericytes

Zhang

Cao²,

Zhang³

et al. 2008

American Journal of Physiology-Renal Physiology

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“…Evidence favoring that hypothesis has been accumulating. Low-dose (10 -100 nM) ouabain enhances Ca 2ϩ release in smooth muscle and endothelium (2, 35) and increases resting cytoplasmic Ca 2ϩ ([Ca 2ϩ ] CYT ) and myogenic tone (35,48).A role for OLF in hypertension is also well supported. Chronic administration of ouabain into rodents induces hypertension (26, 28), and many patients with essential hypertension have high plasma ouabain levels (43).…”

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confidence: 99%

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Chronic ouabain treatment induces vasa recta endothelial dysfunction in the rat

Cao¹,

Payne²,

Lee-Kwon³

et al. 2009

American Journal of Physiology-Renal Physiology

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([Ca 2ϩ ]CYT) signaling. In this study, we examined the expression of the ouabain-sensitive Na-K-ATPase ␣2 subunit in the rat renal vasculature and tested effects of acute ouabain exposure and chronic ouabain treatment on DVR. Immunostaining with antibodies directed against the ␣2 subunit verified its expression in both DVR pericytes and endothelium. Acute application of ouabain (100 or 500 nM) augmented the DVR nitric oxide generation stimulated by acetylcholine (ACh; 10 M). At a concentration of 1 mM, ouabain constricted microperfused DVR, whereas at 100 nM, it was without effect. Acute ouabain (100 nM) did not augment constriction by angiotensin II (0.5 or 10 nM), whereas L-nitroarginine methyl esterinduced contraction of DVR was slightly enhanced. Ouabain-hypertensive (OH) rats were generated by chronic ouabain treatment (30 g ⅐ kg Ϫ1 ⅐ day Ϫ1 , 5 wk). The acute endothelial [Ca 2ϩ ]CYT elevation by ouabain (100 nM) was absent in DVR endothelia of OH rats. The [Ca 2ϩ ]CYT response to 10 nM ACh was also eliminated, whereas the response to 10 M ACh was not. The endothelial [Ca 2ϩ ]CYT response to bradykinin (100 nM) was significantly attenuated. We conclude that endothelial responses may offset the ability of acute ouabain exposure to enhance DVR vasoconstriction. Chronic exposure to ouabain, in vivo, leads to hypertension and DVR endothelial dysfunction, manifested as reduced [Ca 2ϩ ]CYT responses to both ouabain-and endothelium-dependent vasodilators. kidney; medulla; microcirculation; nitric oxide; blood flow "OUABAIN-LIKE FACTORS" (OLF), synthesized by the adrenal gland and hypothalamus, inhibit Na ϩ /K ϩ exchange (19, 46) and activate signaling cascades (6, 7, 44) by binding to Na-KATPase ␣-subunits. In rodents, the ␣1 isoform of Na-KATPase that maintains Na ϩ and K ϩ gradients across cell membranes has very low affinity (K d Ͼ 10 M) for ouabain. In contrast, the ␣2 and ␣3 isoforms have high affinity for ouabain (K d Ͻ 50 nM), but are less abundantly expressed (3, 48). It has been proposed that targeting of the ␣2 isoform to cellular microdomains where ER/SR protrusions abut the plasma membrane (4, 7) may modulate intracellular Na ϩ and reduce Ca 2ϩ extrusion via Na ϩ /Ca 2ϩ exchange to enhance Ca 2ϩ sequestration into ER/SR stores. Evidence favoring that hypothesis has been accumulating. Low-dose (10 -100 nM) ouabain enhances Ca 2ϩ release in smooth muscle and endothelium (2, 35) and increases resting cytoplasmic Ca 2ϩ ([Ca 2ϩ ] CYT ) and myogenic tone (35,48).A role for OLF in hypertension is also well supported. Chronic administration of ouabain into rodents induces hypertension (26, 28), and many patients with essential hypertension have high plasma ouabain levels (43). Transgenic mice in which the ␣2 Na-K-ATPase binding site for ouabain has been mutated are resistant to both ouabain-and ACTH-induced hypertension, supporting a causal role in hypertension for both ouabain and the ␣2 ouabain receptor (12, 13).Detailed mechanisms by which ouabain induces hypertension remain to be elucidated. ...

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Renal Medullary Circulation

Pallone

Edwards

Mattson

2012

Comprehensive Physiology

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The renal medullary microcirculation is a distinctive arrangement of blood vessels that serve multiple functions in the renal medulla. This article begins with a description of the unique anatomy of this vascular bed and the role it plays in transport and countercurrent exchange in the medulla. A segment of the review is then devoted to the important role mathematical modeling has played in the understanding of this vascular bed's function. Succeeding sections focus upon the hematocrit in the vasa recta capillaries and methods utilized to assess blood flow in the renal medulla. An extensive portion of the article is then devoted to the regulation of the medullary circulation, from ion channel architecture to neurohormonal signaling. Finally, we discuss the importance of the renal medullary circulation in the regulation of fluid and electrolyte homeostasis and arterial blood pressure regulation.

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Ouabain modulation of endothelial calcium signaling in descending vasa recta

Cited by 18 publications

References 54 publications

Membrane current oscillations in descending vasa recta pericytes

Membrane current oscillations in descending vasa recta pericytes

Chronic ouabain treatment induces vasa recta endothelial dysfunction in the rat

Renal Medullary Circulation

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