The Ussing chamber technique is a basic method of transport physiology, with the help of which one can determine transport processes using radioactive isotopes or other approaches. Simultaneously, current and potential over the epithelium can be monitored. This allows important conclusions concerning the proteins involved.
With the help of this technique, it is possible to determine whether transport of ammonia across the rumen is mediated by proteins. If the transport occurs in the form of NH₃, no changes in current should occur. However, Ussingchamber measurements show that application of NH₄⁺ leads to changes in current and potential across the ruminal epithelium. Since charged particles cannot diffuse through lipid membranes, NH₄⁺ either has to pass into blood in between the cells, or through the cells via special proteins, ion channels. In order to clarify this, further experiments are required using microelectrode techniques that allow a distinction between the trans- and paracellular pathway. Single ion channels can be investigated using the patch clamp technique.