Changes in morphology and inward rectifier currents in human atrial myocytes depend on culture conditions

Human atrial myocytes were cultured under systematically varied conditions in order to obtain stable cells for future gene manipulation. Transient (I-to) and sustained outward current (I-so) and voltage- and muscarinic receptor-activated inward rectifier K+ currents (I-K1, I-K,I-ACh) were measured in freshly isolated cells and after 5 days in culture. Myocytes were grown on polylysin or laminin in medium with or without 10 % serum (medium+S, medium-S). Cultured myocytes dedifferentiated to a greater extent in medium+S than medium-S, but independent of the chemical nature of the adherence surface. Apparent surface area increased in mediuin+S, Whereas membrane capacitance declined under all culture conditions. I-to of myocytes cultured in medium-S Was increased. Myocytes grown on polylysin and laminin exhibited reduced I-K1 current density. Under all culture conditions, I-K,I-ACh was attenuated with carbachol but hardly affected with sphingosine-1-phosphate as agonists. In conclusion, morphological and electrophysiological changes depended on serum in the culture medium rather than on adherence surface being coated with laminin or polylysin.