Dynamic Effects of Hg2+-induced Changes in Cell Volume

Heo, Jeong Wook; Meng, Fanjie; Sachs, Frederick; Hua, Susan Z.

doi:10.1007/s12013-008-9010-y

Cited by 13 publications

(17 citation statements)

References 55 publications

(88 reference statements)

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“…Figure 5d is a graph of time constants obtained from the swelling curves shown in Figure 5a-c. We and others previously found that a high concentration of Hg 2+ (>50 μM) could rapidly alter the permeability of Na + , K + , and Cl - ions, leading to extraordinary water flow across the cell membrane 30,31. Therefore, we optimized the dose of Hg 2+ to minimize the side effect of Hg 2+ .…”

Section: Resultsmentioning

confidence: 99%

Contribution of Aquaporins to Cellular Water Transport Observed by a Microfluidic Cell Volume Sensor

2008

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Here we demonstrate that an impedance-based microfluidic cell volume sensor can be used to study the roles of aquaporin (AQP) in cellular water permeability and screen AQP-specific drugs. Human embryonic kidney (HEK-293) cells were transiently transfected with AQP3- or AQP4-encoding genes to express AQPs in plasma membranes. The swelling of cells in response to hypotonic stimulation was traced in real time using the sensor. Two time constants were obtained by fitting the swelling curves with a two-exponential function, a fast time constant associated with osmotic water permeability of AQP-expressing cells and a slow phase time constant associated mainly with water diffusion through lipid bilayers in the nontransfected cells. The AQP-expressing cells showed at least 10× faster osmotic water transport than control cells. Using the volume sensor, we examined the effects of Hg2+ and Ni2+ on the water transport via AQPs. Hg2+ inhibited the water flux in AQP3-expressing cells irreversibly, while Ni2+ blocked the AQP3 channels reversibly. Neither of the two ions blocked the AQP4 channels. The microfluidic volume sensor can sense changes in cell volume in real time, which enables perfusion of various reagents sequentially. It provides a convenient tool for studying the effect of reagents on the function and regulation mechanism of AQPs.

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Section: Resultsmentioning

confidence: 99%

Contribution of Aquaporins to Cellular Water Transport Observed by a Microfluidic Cell Volume Sensor

2008

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“…Microscope slides were cut to ~22 mm × 13 mm to fit on the sensor chip and cleaned as previously described [21]. MDCK cells (ATCC) were grown to confluence on the slide in a 35 mm Petri dish using Dulbecco’s Modified Eagle’s Medium (DMEM) containing 10% fetal bovine serum and 1% penicillin-streptomycin.…”

Section: Methodsmentioning

confidence: 99%

Shear-induced Volume Decrease in MDCK Cells

Heo

Sachs

Wang

et al. 2012

Cell Physiol Biochem

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Using a microfluidic cell volume sensor we measured the change in the cell volume of Madin-Darby Canine Kidney (MDCK) cells induced by shear stress. An increase in shear stress from 0.2 to 2.0 dyn/cm² resulted in a volume decrease to a steady state volume ∼ 20 – 30 % smaller than the initial resting cell volume. Independent experiments based on fluorescence quenching confirmed the volume reduction. This shear-induced cell shrinkage was irreversible on the time scale of the experiment (∼ 30 min). Treatment of 0.1 µM Hg²⁺ significantly inhibited the volume decrease, suggesting that the shear-induced cell shrinkage is associated with water efflux through aquaporins. The volume decrease cannot be inhibited by 75 mM TEA, 100 µM DIDS, or 100 µM Gd³⁺ suggesting that volume reduction is not directly mediated by K⁺ and Cl^-channels that typically function during regulatory volume decrease (RVD), nor is it through cationic stretch-activated ion channels (SACs). The process also appears to be Ca²⁺ independent because it was insensitive to intracellular Ca²⁺ level. Since cell volume is determined by the intracellular water content, we postulate that the shear induced reductions in cell volume may arise from increased intracellular hydrostatic pressure as the cell is deformed under flow, which promotes the efflux of water. The increase in internal pressure in a deformable object under the flow is supported by the finite element mechanical model.

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“…The chamber was perfused with test solutions, and the cell volume was monitored in real time. The ratio of the volume change to the resting volume was calculated as previously described (18). A fresh cell culture was used for each trace, and the data represent the first challenge since we have found that RVD rapidly disappears with repeated stimulation (3).…”

Section: Methodsmentioning

confidence: 99%

A mechanosensitive ion channel regulating cell volume

Hua

Gottlieb²,

Heo

et al. 2010

American Journal of Physiology-Cell Physiology

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Cells respond to a hyposmotic challenge by swelling and then returning toward the resting volume, a process known as the regulatory volume decrease or RVD. The sensors for this process have been proposed to include cationic mechanosensitive ion channels that are opened by membrane tension. We tested this hypothesis using a microfluidic device to measure cell volume and the peptide GsMTx4, a specific inhibitor of cationic mechanosensitive channels. GsMTx4 had no effect on RVD in primary rat astrocytes or Madin-Darby canine kidney (MDCK) cells but was able to completely inhibit RVD and the associated Ca(2+) uptake in normal rat kidney (NRK-49F) cells in a dose-dependent manner. Gadolinium (Gd(3+)), a nonspecific blocker of many mechanosensitive channels, inhibited RVD and Ca(2+) uptake in all three cell types, demonstrating the existence of at least two types of volume sensors. Single-channel stretch-activated currents are present in outside-out patches from NRK-49F, MDCK, and astrocytes, and they are reversibly inhibited by GsMTx4. While mechanosensitive channels are involved in volume regulation, their role for volume sensing is specialized. The NRK cells form a stable platform from which to screen drugs that affect volume regulation via mechanosensory channels and as a sensitive system to clone the channel.

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Dynamic Effects of Hg2+-induced Changes in Cell Volume

Cited by 13 publications

References 55 publications

Contribution of Aquaporins to Cellular Water Transport Observed by a Microfluidic Cell Volume Sensor

Contribution of Aquaporins to Cellular Water Transport Observed by a Microfluidic Cell Volume Sensor

Shear-induced Volume Decrease in MDCK Cells

A mechanosensitive ion channel regulating cell volume

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