**Acknowledgements**

We would like to express our gratitude to colleagues at the Institute of Physiology for their support and to Prof. Gerd Leitinger (Medical University Graz) for critical reading of the manuscript.

### **Funding**

This research was funded by the SLOVENIAN RESEARCH AGENCY, grant number P3-0396, I0-0029, N3-0133, and N3-0170.
