Fig. 1.

Schematic illustration of the standard operation procedure for evaluating drug effects. EHTs were subjected to measurements at day 14–21. One day before measurement culture medium was changed. Before evaluation, EHTs were transferred to fresh, preincubated (37 °C, 7 % CO₂, 40 % O₂), serum-free DMEM supplemented with 10 mM HEPES for pH steadiness, and incubated for 45 min. Epinephrine (50 nM) was added and contractile parameters were analyzed by the video optical system. Thereafter, EHTs were transferred to fresh preincubated DMEM, including HEPES plus the first concentration of a drug, and incubated for 45 min. Epinephrine was added, measurements were done and this circuit started again with the second concentration of the drug