Protein G-horseradish peroxidase based method for light-microscope immunocytochemistry. Application to the pituitary gland of the killifish, Fundulus heteroclitus.

Horseradish peroxidase-protein G conjugate was used to localize anti-human luteinizing hormone and anti-human chorionic gonadotropin primary antibodies bound to gonadotropins in paraffin and Historesin embedded sections of Fundulus heteroclitus pituitaries. The sensitivity and specificity of this method and those obtained after the avidin-biotin-peroxidase complex, the streptavidin-biotin-peroxidase complex and the peroxidase-antiperoxidase procedures were compared. The protein G-horseradish peroxidase method gave a clear immunostaining of gonadotrophic cells with virtually no background. Detection efficiency was reduced in comparison with the other techniques. As for the embedding medium, hydrophilic resin Historesin considerably enhanced the structural detail and the resolution of the immunostaining at light-microscope level.