RESUMO

Sertoli cells are essential for the male reproduction system as they provide morphological support and nutrients for germ cells to guarantee ongoing spermatogenesis. The aim of this work was to predict the electrical properties at the plasma membrane that trigger Sertoli cell rapid responses by involving ionic channels. The rapid responses of Sertoli cells in culture were monitored using patch clamp electrical measurement and compared to data obtained using pharmacological tools (from intact seminiferous tubules). A mathematical model was used to define the roles of potassium channels and the ATP-dependent Na+/K+pump in these responses. Mathematical data verification was also performed to determine the resting and hormonal stimulated membrane potentials of Sertoli cells in the intact seminiferous tubules and of Sertoli cells in culture (patch clamp measurements). The prediction of these data based on mathematical modeling demonstrated, for the first time, the involvement of potassium channels and the activation of Na+/K+pump in the hyperpolarization of Sertoli cells and their consequent rapid responses. Moreover, the mathematical analysis showing the involvement of ionic balance in the rapid responses of these cells to hormones, such as follicle-stimulating hormone, is consistent with previous reports obtained using pharmacological techniques in Sertoli cells. Thus, the validation of such data is reliable and represents a first step in the proposition for a mathematical model to predict rapid responses of Sertoli cells to hormonal stimuli.

Assuntos

RESUMO

Magnesium (Mg[Formula: see text] is an essential mineral for several cellular functions. The concentration of this ion below the physiological concentration induces recurrent neuronal discharges both in slices of the hippocampus and in neuronal cultures. These epileptiform discharges are initially sensitive to the application of [Formula: see text]-methyl-D-aspartate (NMDA) receptor antagonists, but these antagonists may lose their effectiveness with prolonged exposure to low [Mg[Formula: see text]], when extracellular Ca[Formula: see text] reduction occurs, typical of ictal periods, indicating the absence of synaptic connections. The study herein presented aimed at investigating the effect of reducing the [Mg[Formula: see text]] during the induction of Nonsynaptic Epileptiform Activities (NSEA). As an experimental protocol, NSEA were induced in rat hippocampal dentate gyrus (DG), using a bath solution containing high-K[Formula: see text] and zero-added-Ca[Formula: see text]. Additionally, computer simulations were performed using a mathematical model that represents electrochemical characteristics of the tissue of the DG granular layer. The experimental results show that the reduction of [Mg[Formula: see text]] causes an increase in the duration of the ictal period and a reduction in the interictal period, intensifying epileptiform discharges. The computer simulations suggest that the reduction of the Mg[Formula: see text] level intensifies the epileptiform discharges by a joint effect of reducing the surface charge screening and reducing the activity of the Na/K pump.

Assuntos

RESUMO

The sodium-potassium pump (Na+/K+ pump) is crucial for cell physiology. Despite great advances in the understanding of this ionic pumping system, its mechanism is not completely understood. We propose the use of a statistical model checker to investigate palytoxin (PTX)-induced Na+/K+ pump channels. We modelled a system of reactions representing transitions between the conformational substates of the channel with parameters, concentrations of the substates and reaction rates extracted from simulations reported in the literature, based on electrophysiological recordings in a whole-cell configuration. The model was implemented using the UPPAAL-SMC platform. Comparing simulations and probabilistic queries from stochastic system semantics with experimental data, it was possible to propose additional reactions to reproduce the single-channel dynamic. The probabilistic analyses and simulations suggest that the PTX-induced Na+/K+ pump channel functions as a diprotomeric complex in which protein-protein interactions increase the affinity of the Na+/K+ pump for PTX.

RESUMO

BACKGROUND: Canine RBCs are expected to have high sodium and low potassium (LK) concentrations. However, some dogs have a low sodium and high potassium (HK) phenotype due to a Na-K pump in the mature RBC membrane. Awareness of this particularity avoids misinterpretation of hyperkalemia in affected dogs. OBJECTIVE: The purpose of this study was to compare the CBCs, serum biochemistry profiles, urinalysis data, and electrocardiography data in HK and LK Akita dogs. METHODS: In this study, the intra-RBC potassium (KRBC) was measured in 48 healthy adult Akita dogs. The HK group included dogs with KRBC concentration at least 5-fold that of plasma, while the LK dogs served as controls. RESULTS: The HK phenotype was determined in 10 dogs (21%). With the exception of higher plasma potassium concentrations in the HK group compared with LK controls (6.6 mmol/L vs 4.4 mmol/L, P < .001), there were no other differences in serum biochemistry variables. In hematology, mean HGB concentration (13.5 vs 15.9, P < .001), PCV (42.9 vs 46.7, P = .009), RBC (6.1 vs 7.4, P < .001), and MCHC (31.3 vs 34.0, P < .001) were significantly lower in the HK group, while MCV (70.0 vs 63.4, P < .001) was higher compared with the LK controls. There were no significant differences in urinalysis or electrocardiography data between groups. CONCLUSIONS: HK Akita dogs showed significant differences in several hematologic variables, as well as higher plasma potassium concentration. Therefore, the HK phenotype should be considered in the interpretation of these variables in this breed.

Assuntos