Improvement of prolactin immunolabelling in osmium-fixed acrylic-embedded pituitary gland.

Immunolabelling of prolactin (PRL) with protein A-colloidal gold complex and tissue fine structure were enhanced after postfixation of pituitary gland with osmium tetroxide and embedment in acrylic momers (LR White). Thin sections were treated with sodium metaperiodate before immunocytochemistry. An intense PRL labelling was detected in secretory granules, Golgi complexes and extracellular accumulation of the hormone. The use of osmium greatly improved the fine structure of the tissue and its stability during acrylic embedment.