Rat Asic2a And Asic3 Ion Channel Electrophysiological Properties Of The Polymer

Acid-sensing ion channels (ASICs) are a kind of cation channels which activated byextracellular acidation, and belong to the corium scdium ion channel family. Till now, seven different subunits of this family were already cloned: ASIC1a, ASIC1b, ASIC1b2, ASIC2a, ASIC2b, ASIC3 and ASIC4. ASICs are distributed extensively in vivo, and their functions are complicatedly. Because of the wide physiological functions and pathologic senses in the aspects of sour taste, sense of touch, sense of pain, etc. ASIC2a and ASIC3 are gradually becoming the hot spots of the research.In the experiment, the express plasmids of rat ASIC2a and ASIC3 which contain the whole sequence were constructed successfully by using molecular biology technique. The cRNA which encode ASIC2a and ASIC3 was injected into Xenopus laevis oocytes. ASIC2a and ASIC3 homopolymer ion channels were expressed on the cell membrane. The currents that induced by H⁺ were recorded by using the two-electrode voltage clamp technique. The pharmacological and gating-kinetic characteristics of the currents were analyzed. The influence of Ca²⁺, Na⁺ and K⁺ on the biological characteristics of ASIC2a and ASIC3 was observed. The findings indicated that: the inward currents could be induced when extracellular pH was decreased. The amplitude of currents increased when pH was decreased. The pH₅₀ value of ASIC2a was 5.12 and the pH₅₀ value of ASIC3 was 5.83. The inward currents of ASIC2a had steady-state inactivation, the inward currents of ASIC3 were composed by rapid and steady-state inactivation. When Ca²⁺ in extracellular fluids was increased, the amplitude of H⁺-induced currents was decreased. Ca²⁺ in extracellular fluids had inhibitive effects on ASIC2a and ASIC3, the IC50 values were 11.98mmol/L and 9.16mmol/L. Beside the permeability to Na⁺, ASIC2a and ASIC3 also had the permeability to K⁺ in certain degree.In the experiment, Xenopus laevis oocytes used as an expression vector, and the express cell system of ASIC2a and ASIC3 homopolymer ion channels was established successfully. The electrophysiology characteristics and the influence of different ions to the functions about ASIC2a and ASIC3 were studied systematically. The results not only in favour of the understanding of biology characteristics about acid-sensing ion channels, but also the system could provide a technique platform of screening and evaluation for the new medicines targeting ASICs.