The quantification of the histochemical protein staining with 2-hydroxy-1-naphthaldehyde (HNA) demonstrating primary amino groups of proteins.

The usefulness of the HNA-pH4-1d staining, which histochemically demonstrates primary protein amino groups under the conditions used, for the microphotometric quantification of proteins was investigated. A correlation (r = 0.986) has been found between the mean protein contents of fresh frozen and fixed sections prepared from different tissues of rats and the corresponding mean integrated extinction values determined histophotometrically after HNA-pH4-1d staining. A histophotometric extinction of E = 0.284 corresponded to 10(-12) g protein. The mean integrated extinction values determined cytophotometrically of different single cells and nuclei stained using the tetrazonium coupling method for proteins correlated (r = 0.989) with corresponding extinction values measured after HNA-pH4-1d staining. A cytophotometric extinction after HNA-pH4-1d staining of E = 0.130 correspond to 10(-12) g protein.