Principle of Bioassay of Histamine
Histamine causes contraction of smooth muscle, notably the guinea pig ileum, and also has vasodilatory and other effects.
The classic bioassay measures the contraction of the isolated guinea pig ileum.
Method
Guinea Pig Ileum Assay
Procedure:
Isolate a segment of guinea pig ileum, mount it in an organ bath.
Add graded doses of standard histamine and measure the contraction. Wash out between doses.
Similarly, test the unknown sample in graded doses.
Potency Determination: Plot dose-response curves (e.g., % maximal contraction vs. dose). Compare the EC50 (effective concentration for 50% maximal response) for standard vs. test. (Bioassay of Histamine)