Exprese izoforem Na+-K+ ATPázy v srdeční buňce

Cor Vasa 2004, 45(10):492-496

Expression of Na⁺-K⁺ ATPase isoforms in the myocyte

Petr Ošťádal^*, Martin Mates: Kardiologická klinika, Fakultní nemocnice Motol a 2. lékařská fakulta Univerzity Karlovy, Praha, Česká republika

Na⁺-K⁺ ATPase is a key enzyme of animal cells, responsible for the exchange of Na⁺ and K⁺ across the cell membrane. Through maintenance of transmembrane ionic gradient for Na⁺ and K⁺, the enzyme is largely involved in calcium metabolism (via the Na⁺-Ca²⁺ exchanger), including the role of Ca²⁺ in myocardial contraction. The energy accumulated in the transmembrane gradient is, however, used also for numerous different processes, including pH regulation (via the Na⁺-H⁺ exchanger) and transportation of glucose, amino acids, and vitamins. It is well known that Na⁺-K⁺ ATPase activity can be altered significantly under various pathological conditions; it is, however, often not clear whether Na⁺-K⁺ ATPase plays a role in the pathogenic mechanisms or is just their consequence. The importance of Na⁺-K⁺ ATPase for clinical cardiology results also from the fact that the effect of one of the oldest currently used drugs, cardiac glycosides, is based on Na⁺-K⁺ ATPase inhibition. Recently, the molecular structure of the enzyme has also been described; with four isoforms, α₁, α₂, α₃ and β₁ shown to be primarily expressed in the heart. The isoforms differ in various properties, including enzyme activity, sensitivity to cardiac glycosides, and localization of expression in the cardiac muscle. Isoform expression also seems to be significantly altered under different pathological conditions.