Measurement of Calcium Flux and Intracellular Sodium by Ion-Selective Microelectrodes

Author(s):  
Donald M. Bers ◽  
Michael J. Shattock
1990 ◽  
Vol 95 (3) ◽  
pp. 499-522 ◽  
Author(s):  
R P Kline ◽  
L Zablow ◽  
I S Cohen

The role of the Na/Ca exchanger in the control of cellular excitability and tension development is a subject of current interest in cardiac physiology. It has been suggested that this coupled transporter is responsible for rapid changes in intracellular calcium activity during single beats, generation of plateau currents, which control action potential duration, and control of intracellular sodium during Na/K pump suppression, which may occur during terminal states of ischemia. The actual behavior of this exchanger is likely to be complex for several reasons. First, the exchanger transports two ionic species and thus its instantaneous flux rate depends on both intracellular sodium and calcium activity. Secondly, the alteration in intracellular calcium activity, which is caused by a given transmembrane calcium flux, and which controls the subsequent exchanger rate, is a complex function of available intracellular calcium buffering. The buffers convert the ongoing transmembrane calcium fluxes into changes in activity that are a small and variable fraction of the change in total calcium concentration. Using a number of simple assumptions, we model changes in intracellular calcium and sodium concentration under the influence of Na/Ca exchange, Na/K ATPase and Ca-ATPase pumps, and passive sodium and calcium currents during periods of suppression and reactivation of the Na/K ATPase pump. The goal is to see whether and to what extent general notions of the role of the Na/Ca exchanger used in planning and interpreting experimental studies are consistent with its function as derived from current mechanistic assumptions about the exchanger. We find, for example, that based on even very high estimates of intracellular calcium buffering, it is unlikely that Na/Ca exchange alone can control intracellular sodium during prolonged Na/K pump blockade. It is also shown that Na/Ca exchange can contaminate measurements of Na/K pump currents under a variety of experimental conditions. The way in which these and other functions are affected by the dissociation constants and total capacity of the intracellular calcium buffers are also explored in detail.


2018 ◽  
Vol 2 (3) ◽  
pp. 184-201
Author(s):  
George D Glinos ◽  
Irena Pastar ◽  
Marjana Tomic-Canic ◽  
Rivka C Stone

Darier disease (DD) is an autosomal dominant keratinizing genodermatosis that manifests clinically with red-brown pruritic papules in a seborrheic distribution often in association with palmoplantar pits and dystrophic nail changes. It is caused by mutation in ATP2A2 which encodes a sarco/endoplasmic reticulum calcium ATPase isoform 2 (SERCA2) pump that regulates calcium flux. Consequent alteration of intracellular calcium homeostasis is thought to impair trafficking of cellular adhesion proteins and to lead to aberrant keratinocyte differentiation, contributing to the characteristic histopathologic features of acantholysis and dyskeratosis in DD, though the precise mechanisms are incompletely understood. Previous studies have identified defective localization of desmosomal attachment proteins in skin biopsies and cultured keratinocytes from DD patients, but reports of effects on adherens junction proteins (including calcium-dependent E-cadherin) are conflicting. Here we describe a case of DD presenting with characteristic clinical and histologic features in which we performed immunofluorescence staining of four adherens junction-associated proteins (E-cadherin, α-catenin, β-catenin, and vinculin). In lesional (acantholytic) DD skin, we identified loss of distinctive bright membranous staining that was present at the periphery of keratinocytes throughout the epidermis in the healthy skin of a matched donor. Perilesional (non-acantholytic) portions of DD skin partially recapitulated the normal phenotype. Our findings support a role for SERCA2 dysfunction in impaired assembly of adherens junctions, which together with defective desmosomes contribute to acantholysis in DD.


1987 ◽  
Vol 253 (6) ◽  
pp. R917-R921
Author(s):  
S. Sabatini ◽  
N. A. Kurtzman

Unidirectional 45Ca fluxes were measured in the turtle bladder under open-circuit and short-circuit conditions. In the open-circuited state net calcium flux (JnetCa) was secretory (serosa to mucosa) and was 388.3 +/- 84.5 pmol.mg-1.h-1 (n = 20, P less than 0.001). Ouabain (5 X 10(-4) M) reversed JnetCa to an absorptive flux (serosal minus mucosal flux = -195.8 +/- 41.3 pmol.mg-1.h-1; n = 20, P less than 0.001). Amiloride (1 X 10(-5) M) reduced both fluxes such that JnetCa was not significantly different from zero. Removal of mucosal sodium caused net calcium absorption; removal of serosal sodium caused calcium secretion. When bladders were short circuited, JnetCa decreased to approximately one-third of control value but remained secretory (138.4 +/- 54.3 pmol.mg-1.h-1; n = 9, P less than 0.025). When ouabain was added under short-circuit conditions, JnetCa was similar in magnitude and direction to ouabain under open-circuited conditions (i.e., absorptive). Tissue 45Ca content was approximately equal to 30-fold lower when the isotope was placed in the mucosal bath, suggesting that the apical membrane is the resistance barrier to calcium transport. The results obtained in this study are best explained by postulating a Ca2+-ATPase on the serosa of the turtle bladder epithelium and a sodium-calcium antiporter on the mucosa. In this model, the energy for calcium movement would be supplied, in large part, by the Na+-K+-ATPase. By increasing cell sodium, ouabain would decrease the activity of the mucosal sodium-calcium exchanger (or reverse it), uncovering active calcium transport across the serosa.


Cell Calcium ◽  
2021 ◽  
Vol 94 ◽  
pp. 102356 ◽  
Author(s):  
William M. Rosencrans ◽  
Megha Rajendran ◽  
Sergey M. Bezrukov ◽  
Tatiana K. Rostovtseva

2021 ◽  
Vol 22 (11) ◽  
pp. 5863
Author(s):  
Giuseppe Palmiero ◽  
Arturo Cesaro ◽  
Erica Vetrano ◽  
Pia Clara Pafundi ◽  
Raffaele Galiero ◽  
...  

Heart failure (HF) affects up to over 20% of patients with type 2 diabetes (T2DM), even more in the elderly. Although, in T2DM, both hyperglycemia and the proinflammatory status induced by insulin resistance are crucial in cardiac function impairment, SGLT2i cardioprotective mechanisms against HF are several. In particular, these beneficial effects seem attributable to the significant reduction of intracellular sodium levels, well-known to exert a cardioprotective role in the prevention of oxidative stress and consequent cardiomyocyte death. From a molecular perspective, patients’ exposure to gliflozins’ treatment mimics nutrient and oxygen deprivation, with consequent autophagy stimulation. This allows to maintain the cellular homeostasis through different degradative pathways. Thus, since their introduction in the clinical practice, the hypotheses on SGLT2i mechanisms of action have changed: from simple glycosuric drugs, with consequent glucose lowering, erythropoiesis enhancing and ketogenesis stimulating, to intracellular sodium-lowering molecules. This provides their consequent cardioprotective effect, which justifies its significant reduction in CV events, especially in populations at higher risk. Finally, the updated clinical evidence of SGLT2i benefits on HF was summarized. Thus, this review aimed to analyze the cardioprotective mechanisms of sodium glucose transporter 2 inhibitors (SGLT2i) in patients with HF, as well as their clinical impact on cardiovascular events.


1985 ◽  
Vol 260 (23) ◽  
pp. 12740-12743 ◽  
Author(s):  
B M Rayson ◽  
R K Gupta
Keyword(s):  

2021 ◽  
Vol 11 (6) ◽  
pp. 2846
Author(s):  
Jong-ryul Choi ◽  
Juyoung Park

Techniques that increase the permeability of the cell membrane and transfer drugs or genes to cells have been actively developed as effective therapeutic modalities. Also, in line with the development of these drug delivery techniques, the establishment of tools to verify the techniques at the cellular level is strongly required. In this study, we demonstrated an optical imaging platform integrated with an ultrasound application system to verify the feasibility of safe and efficient drug delivery through the cell membrane using ultrasound-microbubble cavitation. To examine the potential of the platform, fluorescence images of both Fura-2 AM and propidium iodide (PI) to measure calcium flux changes and intracellular PI delivery, respectively, during and after the ultrasound-microbubble cavitation in the cervical cancer cell were acquired. Using the optical imaging platform, we determined that calcium flux increased immediately after the ultrasound-microbubble cavitation and were restored to normal levels, and fluorescence signals from intracellular PI increased gradually after the cavitation. The results acquired by the platform indicated that ultrasound-microbubble cavitation can deliver PI into the cervical cancer cell without irreversible damage of the cell membrane. The application of an additional fluorescent imaging module and high-speed imaging modalities can provide further improvement of the performance of this platform. Also, as additional studies in ultrasound instrumentations to measure real-time cavitation signals progress, we believe that the ultrasound-microbubble cavitation-based sonoporation can be employed for safe and efficient drug and gene delivery to various cancer cells.


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