In this lab, we determined how much voltage develops across the membrane of frog skin in order to keep the frogs body osmoregulated from the surrounding environment. As we all know, different animals use different means of keeping their ion concentrations regulated fom the surrounding environment; salt glands in marine birds and chloride cells in fish gills. In frogs, as well as other amphibians, the skin is not only a transport epithelium but a major osmoregulatory organ. They actively transport Na and Cl from fresh water into their bodies.

In this experiment we want to measure the voltage across the frog skin membrane when the skin is submerged in different concentration solutions:

The seet-up used for the measurement of the frog skin is pretty cool. Unfortunately, the frog had to be sacrificed for the means of science in order to use it. The way the voltage across the skin is read is simple. The electrodes actually pick up the voltage difference across the membrane and we also measure the amount of microamps required in order to cause the membrane to actively transport (1 microamp= 63*10 moles of Na). Since the equipment decided not to work for our lab, here is the data that Dr. Allen obtained:

As you can see from the data, when the solution outside the membrane is equal to that inside the mambrane, the transmembrane voltage is low; meaning little active trnasport. Where as the transmembrane voltage when the skin is submerged in 0.1% concentration solution is high and little microamps are required to get it so.

Here is a graph that shows the different voltages against the outside concentrations.