The investigation of isolated cardiomyocytes has the disadvantage that cells are no longer coupled via gap junctions and therefore may loose physiological properties. Especially in pig atrium isolation of cells leads to a substantial depolarization of the membrane potential. Patch clamp measurements on single pig atrial cardiomyocytes revealed a resting membrane potential of -463 mV (n=23), whereas recordings from pig atrial trabecular muscle showed -731 mV (n=17). The aim of the present study was to establish precision-cut heart slices where the cells are coupled in an organotypic manner. The technique was already applied to embryonic and adult mouse ventricular slices (Cell Physiol Biochem. 2005, 16, 127–32). We extended the method to slices from pig atrium and ventricle as well as guinea pig ventricle. Using a vibratome, heart slices of 300 mm thickness were cut. A live-dead staining exhibited the viability of cells throughout the slice whereas damaged cells were restricted to the cutting surface. Action potentials from pig atrial slices were assessed by sharp electrode measurement and showed the following parameters: membrane potential -771 mV, APD₉₀ 1606 ms, APD₂₀ 415 ms, amplitude 963 mV (n = 18, pacing with 2.5 Hz). The action potential of pig ventricular slices was characterized by a membrane potential of -842 mV, an APD₉₀ of 2188 ms, an APD₂₀ of 1129 ms and an amplitude of 1094 mV (n = 7, pacing with 2.5 Hz). In guinea-pig ventricular slices we tested the effect of various tool compounds on the action potential. We found that blocking I_Kr with dofetilide elongated the action potential duration (APD₉₀) with a half-maximal concentration of 18 nM. The elongation was even more pronounced when repolarisation reserve was attenuated by inhibiting I_Ks with the specific blocker HMR1556. K_ATP channels could be activated with rilmakalim leading to a shortening of APD₉₀ from 1897 ms to 236 ms (n = 5). This was largely reversed with glibenclamide (IC₅₀=0.16 mM). Inhibition of L-type Ca²⁺ channels with nifedipine shortened APD₉₀ with an IC₅₀ of 0.96 mM. In summary, the results show that it is possible to produce viable heart slices from different species (pig and guinea-pig) as well as from different organ regions (ventricle and atrium). Especially in pig atrium coupling of the cells in the slice preparation prevents the depolarization of membrane potential seen in isolated cardiomyocytes.

Supported by the BMBF project Human Heart Models (01GG0711).