Figure 7 shows the time course of Vt/V0, EqCl, EqK, Vm and Jnet when K+ permeability is decreased (reduced PK), thus mimicking cells exposed to Ba2+, versus control conditions (control PK). retinal Mller cell line (MIO-M1) under different extracellular ionic conditions, and to study a possible association between RVD and changes in Vm. Cell volume and Vm changes were evaluated using fluorescent probe techniques and a mathematical model. Results show that cell swelling and subsequent RVD were accompanied by Vm depolarization followed by repolarization. This response depended on the composition of extracellular media. Cells exposed to a hypoosmotic solution with reduced ionic strength underwent maximum RVD and had a larger repolarization. Both of these responses were reduced by K+ or Cl? channel blockers. In contrast, cells facing a hypoosmotic solution with the same ionic strength as the isoosmotic solution showed a lower RVD and a smaller repolarization and were not affected by blockers. Together, experimental and simulated data led us to propose that the efficiency of the RVD process in Mller glia depends not only on the activation of ion channels, but is also strongly modulated by concurrent changes in the membrane potential. The relationship between ionic fluxes, changes in ion permeabilities and ion concentrations Call leading to changes in VmC define the success of RVD. Introduction Glial cells in the sensory retina (Mller cells) are mainly involved in controlling osmotic and ionic homeostasis [1], [2]. During intense neuronal activity, retinal cells can be surrounded by a hypoosmotic environment, since light-evoked changes in the ionic composition of the extracellular fluid cause a decrease in osmolarity, thus favoring glial swelling [3]. In most cell types this increase in cell volume is followed by a regulatory volume decrease response (RVD) partially mediated by the activation of K+ and anion channels [4], [5], [6]. However, only a few studies have evaluated the mechanisms underlying cell volume regulation in Mller cells [7], [8]. It has been reported that Mller cells show an effective control of cell volume, that prevents cell swelling, probably due to the presence of K+ channels Kir 4.1. The expression of these channels is altered in different pathologies such as retinal ischemia, ocular inflammation and diabetes, as well as in organ cultures [9], [10], [11], [12]. Changes in the extracellular ion composition of the retina during neural activity also cause changes in transmembrane potential (Vm) and in the chemical gradients of most of the ions that determine RVD. In addition, the activation of ion channels during RVD may also alter Vm. However, to our knowledge, no studies have investigated the putative link between cell volume regulation and Vm in these cells. The channels involved in the RVD response have been studied in different cell types, usually by evaluating changes in cell volume with and without blockers. The identification and characterization of these channels is typically performed through FG-2216 excised or whole cell patch clamp studies [13], [14], [15]. Though these methods undeniably offer important and reliable information on conductance changes during cell swelling, they fail to do so FG-2216 during cell volume regulation, since they do not preserve cell membrane integrity nor intracellular medium composition. This could explain the reason why only a few reports have been able to evaluate the RVD response in a more physiological Mouse monoclonal to LSD1/AOF2 context [16], [17], [18]. The aim of the present work is to characterize, for the first time, FG-2216 the RVD response in a retinal Mller cell line (MIO-M1) under different extracellular ionic conditions and to evaluate a possible association between RVD and changes in Vm. Cell volume and Vm changes were measured using fluorescent probe techniques. We also developed a mathematical model that provides information on electrochemical ion gradients and solutes fluxes during FG-2216 the RVD response. Our results show that cell swelling and subsequent RVD is accompanied by Vm depolarization followed by repolarization. However, this RVD response depends closely on the composition of extracellular media. Although K+ and Cl? channels do play an important role in.