Field and action potential recordings in heart slices: correlation with established in vitro and in vivo models.

BACKGROUND AND PURPOSE: Action potential (AP) recordings in ex vivo heart preparations constitute an important component of the preclinical cardiac safety assessment according to the ICH S7B guideline. Most AP measurement models are sensitive, predictive and informative but suffer from a low throughput. Here, effects of selected anti-arrhythmics (flecainide, quinidine, atenolol, sotalol, dofetilide, nifedipine, verapamil) on field/action potentials (FP/AP) of guinea pig and rabbit ventricular slices are presented and compared with data from established in vitro and in vivo models. EXPERIMENTAL APPROACH: Data from measurements of membrane currents (hERG, I(Na) ), AP/FP (guinea pig and rabbit ventricular slices), AP (rabbit Purkinje fibre), haemodynamic/ECG parameters (conscious, telemetered dog) were collected, compared and correlated to complementary published data (focused literature search). KEY RESULTS: The selected anti-arrhythmics, flecainide, quinidine, atenolol, sotalol, dofetilide, nifedipine and verapamil, influenced the shape of AP/FP of guinea pig and rabbit ventricular slices in a manner similar to that observed for rabbit PF. The findings obtained from slice preparations are in line with measurements of membrane currents in vitro, papillary muscle AP in vitro and haemodynamic/ECG parameters from conscious dogs in vivo, and were also corroborated by published data. CONCLUSION AND IMPLICATIONS: FP and AP recordings from heart slices correlated well with established in vitro and in vivo models in terms of pharmacology and predictability. Heart slice preparations yield similar results as papillary muscle but offer enhanced throughput for mechanistic investigations and may substantially reduce the use of laboratory animals.

Reduction of hERG potassium currents by hyperosmolar solutions.

We investigated the effects of hyperosmolar solutions on human ether-a-go-go related gene (hERG) potassium currents in chinese hamster ovary (CHO) cells. The addition of d-mannitol to the external solution caused cell shrinkage and reduced current amplitude. The effects were at least partially reversible. Exposure to 108 mM mannitol decreased current amplitude by 57+/-13%. Major effects on current-voltage relations were not observed. Exposure to 308 mM mannitol reduced the current by 89+/-5%, i.e. comparable to the block induced by 1 microM of the selective hERG channel blocker E-4031. We conclude that the investigation of hyperosmolar drug formulations requires control solutions of comparable osmolarity to separate specific drug effects from non-specific effects of hyperosmolarity.

[Potency Testing of Erysipelas Vaccines in Mice. ELISA vs. Challenge]

Vaccines are widely used for the prophylaxis of swine erysipelas. According to national pharmacopoiea requirements, potency of these biologicals has to be tested in a mouse challenge model. Many animals are needed and the test causes much suffering. The development of an enzyme linked immunosorbet assay (ELISA) using an alkaline extract of Erysipelothrix rhusiopathiae as antigen for coating the microtitre plate allows us to measure antibody titres in the serum of vaccinated mice. By comparing the antibody titres of vaccinated mice with the results of the animal challenge model it could be demonstrated that the in vitro method gives reliable and reproducible data which correlate with the results of the in vivo model. The ELISA offers the possibility to refine the currently used animal test, by replacing the challenge procedure and reducing the number of animals.