Physiology Problem 1

Calculate the ECF volume using:

• Amount of Inulin injected = 4 mg
• Inulin conc. in plasma at the end of 1 hr. = 0.02 mg/100 ml (0.0002 mg/ml)
• Amount of Inulin excreted in 1 hr. = 1.2 mg

1. Comment on the value.
2. Why is Inulin used?
3. What other substance can be used to determine ECF volume?

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A1. ECF volume is normal.

A2. Inulin diffuses more evenly throughout all the sub-compartments of ECF.

A3. Radioactive Sodium, Chloride, Bromide, Sulphate and Thiosulphate, Raffinose, Sucrose, Mannitol.