The in situ localization of folic acid.

A histochemical azo-coupling method for localizing folic acid in situ is described. Cat and rat liver, kidney, bone marrow and brain were found to be rich in folic acid; stomach, intestine, salivary glands, and blood contained less. Folic acid was localized in the cytoplasm of tissues having a very active metabolism, but in the nucleus of highly specialized cells such as neurons.