Question.

Which is better as a control for glycogen staining: alpha-amylase or human saliva?

Answer.

The bought enzyme (10 mg/ml, in water) takes about 10 minutes to remove the stainable glycogen from a section of liver. The enzyme is not very expensive.

Saliva is free, and it takes about 30 minutes, but some people don't enjoy spitting, or even dribbling, onto their slides. A theoretical disadvantage of spit is that it contains plenty of digestive enzymes additional to amylase (= diastase), notably ribonuclease and various proteases. However, these are unlikely to remove substances with the same staining properties as glycogen.

John A. Kiernan
London, Canada
(kiernan[AT]uwo.ca)