The expression of neutral glycosphingolipids and gangliosides has been studied in human skeletal and heart muscle using indirect immunofluorescence microscopy. Transversal and longitudinal cryosections were immunostained with specific monoclonal and polyclonal antibodies against the neural glycosphingolipids lactosylceramide, globoside, Forssman glycosphingolipid, gangliotetraosylceramide, lacto-N-neotetraosylceramide and against the gangliosides GM3(Neu5Ac) and GM1(Neu5Ac). To confirm the lipid nature of positive staining, control sections were treated with methanol and chloroform:methanol (1:1) before immunostaining. These controls were found to be either negative or strongly reduced in fluorescence intensity, suggesting that lipid bound oligosaccharides were detected. In human skeletal muscle, lactosylceramide was found to be the main neutral glycosphingolipid. Globoside was moderately expressed, lacto-N-neotetraosylceramide and gangliotetraosylceramide were minimally expressed and Forssman glycosphingolipid was not detected in human skeletal muscle. The intensities of the immunohistological stains of GM3 and GM1 correlated to the fact that GM3 is the major ganglioside in skeletal muscle whereas GM1 is expressed only weakly. In human heart muscle globoside was the major neutral glycosphingolipid. Lactosylceramide and lacto-N-neotetraosylceramide were moderately expressed, gangliotetraosylceramide was weakly expressed and the Forssman glycosphingolipid was not expressed at all in cardiac muscle. GM3 and GM1 were detected with almost identical intensity. All glycosphingolipids were present in plasma membranes as well as at the intracellular level.
