Regulation Of Isoprenaline On Na～+, K～+-ATPase In Guinea-pig Ventricular Myocytes And Its Underlying Mechannisms

Na+,K+-ATPase (Na+,K+-pump) is an integral protein in the plasma membrane of all mammalian cells. Its primary role is to maintain intcellular low sodium and high potassium. During each cycle of the Na+,K+-pump activity it extrudes 3 Na+ from the cell and moves 2 K+ into the cell with utilization of 1 ATP. Thus, a pump cycle can produce a net outward pump current(I p). In physiological condition, Na+,K+-ATPase consists of twoαand twoβsubunit.αsubunit is a catalytic subunit, which contains the binding sites for ATP, Na+, K+, and its specific inhibitor ouabain. Four different isoforms (α1,α2,α3,α4) of theαsubunit have been discovered, and they express in a tissues- and species-specific manner. Theαsubunits are the products of different genes, which indepedently transcribe into their respective mRNA.α1 isoform is expressed ubiquitously among tissues, whereas theα2 andα3 isoform mainly exist in excitable cells. Theα1 has a distinctly lower affinity for ouabain than theα2 isoform andα3 isoform. The Na+,K+-ATPase is subjected to both short- and long-term regultion by a varity of hormones and...