A mathematical model of the calcium transient in urinary bladder smooth muscle cells

Abstract

An increase in cytoplasmic calcium (Ca(2+)) concentration ([Ca(2+)]i) is a prerequisite for the contraction of detrusor smooth muscle (DSM) cells . The increase in [Ca(2+)]i is accomplished by Ca(2+) entry mainly via voltage dependent L-type Ca(2+) channel and Ca(2+) release from intracellular stores. We report here a simulation of the processes that regulate intracellular Ca(2+) and their dependence on Ca(2+) concentration. Based on experimentally recorded data, mathematical equations for Ca(2+) current (generated mainly by L-type Ca(2+) channel) are developed along with representation of Ca(2+)ATPase pump currents. The plasma membrane Ca(2+)ATPase (PMCA) pump and sarco/endoplasmic reticulum Ca(2+)ATPase (SERCA) pump are responsible for lowering [Ca(2+)]i which leads to relaxation of smooth muscle. Our model simulates Ca(2+) current, action potential and the Ca(2+) transient response so as to reasonably mimic the experimental recordings. In novel findings, currents produced by PMCA and SERCA along with their amplitude and waveform pattern under voltage clamp condition have been predicted for DSM cells. The model has further been used to produce the Ca(2+) transient which results because of L-type Ca(2+) channel, Ca(2+) release from intracellular store, PMCA, SERCA and presence of buffer in the cytoplasm. To explore the model further, Ca(2+) transient decay rate in control condition is compared to the decay rate reached when PMCA and SERCA are inhibited. We conclude that this model can be used to describe the Ca(2+) transient response produced by the DSM cell in response to depolarization of cell membrane.

Non-rigid Multi-Modal Medical Image Registration Based on Improved Maximum Mutual Information PV Image Interpolation Method

“…PV image interpolation ( 40 ) is a common registration method in medical research, which is convenient in updating the joint histogram of two images. Suppose that the reference image is R, and the image to be registered is F for any point p on image F. After transforming T , the point q in the reference image R is corresponding, that is, q = T ( p ).…”

A Mathematical Model of Spontaneous Action Potential Based on Stochastics Synaptic Noise Dynamics in Non-Neural Cells

“…It also serves as a model where background activity imitates continuous synaptic conductance activities for modulating neuron firing rates and patterns [32][33][34]. We have refined these models, incorporating precise adjustments to simulate the modulatory impact of stochastic excitatory synaptic conductance on spontaneous electrical activities within the previously published biophysically detailed DSM cell models [35][36][37][38][39]. The membrane can depolarize when positive ions accumulate in the intracellular space as a result of the opening of particular ion channels: nonspecific cation channels (NSCCs), voltage-dependent calcium channels (VDCCs), and voltage-gated sodium channels (Navs) [4].…”

In Silico Electrophysiological Investigation of Transient Receptor Potential Melastatin-4 Ion Channel Biophysics to Study Detrusor Overactivity

“…While computational models for various types of smooth muscle cells, such as intestinal [63], uterine [64][65][66], ureter [67][68][69], jejunal [70], vas deferens [71][72][73][74], gastric [75,76], mesenteric [77], small bowel [78], urethra [79,80], and arterial [81] smooth muscle cells, have been developed, models for DSM cells are relatively underdeveloped. The models published on DSM electrophysiology have yet to explore the modulatory properties of TRPM4 ion channels in DSP action potentials [82][83][84][85][86][87][88]. The present in silico model aims to elucidate the biophysical mechanisms underlying the DSM electrophysiology, aiming to investigate the impact of the TRPM4 ion channel on the firing rate of DSM action potentials.…”