Binding of antibiotics to glycoproteins of the vitelline and fertilization envelopes of cherry salmon eggs.

The binding of antibiotics (gentamicin, oleandomycin and chloramphenicol) to vitelline and fertilization envelopes and their extracts was investigated by immunohistochemical and immunocytochemical techniques and immunoblot analysis using mature and artificially activated eggs of the fish Oncorhynchus masou. Binding of antibiotics was detected in the vitelline and fertilization envelope outermost layers, the fertilization envelope inner surface and cortical alveolus exudates, with differences in immunoreactive intensity and deposition. The fertilization envelope outermost layer had the capacity to bind much greater amounts of the antibiotics than the vitelline envelope outermost layer. The greater capacity was caused by the deposition of cortical alveolus exudates, which were known to be responsible for functional roles of protection against bacteria, fungi and noxious materials. Treatment of the vitelline and fertilization envelopes with neuraminidase markedly reduced the binding of gentamicin and chloramphenicol but slightly increased that of oleandomycin; binding of the latter to the vitelline and fertilization envelope outermost layers was considerably reduced after treatment with alpha-fucosidase. Treatment of the two envelopes with alpha-mannosidase, beta-galactosidase or beta-D-glucosaminidase did not cause any alteration in immunoreactive intensity or number of immunoreactive deposits. Immunoblot analysis of the vitelline or fertilization envelope extracts indicated that many of the antibiotic-binding substances were glycoproteins, and several major bands were bound by all three antibiotics. These results suggest that the vitelline or fertilization envelopes may have the ability to protect the egg itself, or the embryo, respectively, by trapping antibiotics, and the trapping may be related to the presence of carbohydrate moieties, such as sialyl or fucosyl residues.