ATS is a monogenic inherited disease characterized by dyskalemic periodic paralysis, heart arrhythmia and skeletal dysmorphia. In about 60 % of patients loss-of-function mutations in the gene, coding for the ubiquitously expressed inward rectifying potassium channel, Kir2.1 have been described. The periodic paralysis of ATS can be either hypo-, normo- or hyperkalemic. The phenotype of the paralysis seems to be independent from the mutation itself. We hypothesize, that other membrane properties than inward rectification account for this phenomenon.

By use of a computer simulation, we tested how ion channels and pumps affect the extracellular K+ concentration. The model consists of variable compartments. The cell membrane contains voltage-gated Na+ and K+ conductances, a Cl- leak and an inward rectifying K+ conductance, as well as a Na+ /K+ -pump.

At a given intracellular amount and concentration of anions, the intracellular Na+ concentration ([Na+ ]i) in the steady state determines the distribution of K+ . [Na+ ]i levels off, when the pump flux compensates for passive inward fluxes.

Since Na+ channels and the Na+ /K+ -pumps are extensively regulated, e. g. by regulating proteins, there are various options for interindividual variations to evolve.