An experiment

Question

In the context of an experiment in school.
It’s known that CF patients loose more salt than healthy people. This is due to the defect in the CFTR-protein.
I would like to prone my experiment as follows:
First I measure the amount of salt in the blood of patients with CF before they have eaten. Then I have them drink a salty liquid. For instance a sports liquid and then I measure the salt content again. If the patient still loses the same amount of salt, drinking this salty liquid will have a positive effect on his salt balance.
I just don’t know where I should measure the salt content given the limited possibilities in the lab at our school. I don’t think a sweat test will be an option. Should I measure it in the saliva or in the urine?

Answer

Dear questioner
Patients with CF indeed do lose more salt than healthy people. This salt loss in the sweat is because the salt cannot be reabsorbed through the sweat duct. The salt content in sweat is not really determined to a great extent by the salt intake. When a patient with CF will have insufficient salt intake it will first be measurable in the urine. Extra amounts of salts are lost by the urine. In the case of low salt reserves the body will keep all the salt and hardly excrete any via the urine. Only after that stage the salt content in the blood will decrease. These phenomenon is well known and it’s absolutely not appropriate to try and set up an experiment in people in the context of a test to be done at school. Human experiments have to be done according to very strict guidelines. They need to be necessary (study an aspect that has not been studied before) and need to be done in a safe environment. You need to have an approval of an ethics committee.
Therefore we need totally to discourage you to do any such experiment.
Prof. Kris De Boeck

02.05.2012