Formaldehyde-amine fixatives for immunocytochemistry of cultured Xenopus myocytes

Although formaldehyde is commonly used in immunocytochemical studies, this fixative can cause distortions in cell structure. We tested the possibility that adducts of formaldehyde and primary amines could be used as improved fixatives for immunolabeling studies of cultured cells. A variety of primary amines were reacted with formaldehyde and applied to cultured Xenopus muscle cells, after which the cultures were labeled for immunofluorescence. Amine-formaldehyde fixatives improved structural preservation of the myocytes as compared with formaldehyde alone. The extent of improvement depended on the amine tested; the best results were obtained using cyclohexylamine. Immunofluorescence localization of a variety of antigens was better in myocytes fixed with cyclohexylamine-formaldehyde than in cells fixed with formaldehyde alone. In addition, the fixative provided good ultrastructural preservation of cytoskeletal structures and permitted immunogold labeling for alpha-actinin by use of pre-embedding labeling techniques.