Chromogranin A, B and C: immunohistochemical localization in ovine pituitary and the relationship with hormone-containing cells.

Chromogranins A, B and C, three distinct groups of proteins found in bovine chromaffin granules, were also found to be present in the pituitary using immunoblotting techniques. Their distribution was therefore studied in the normal ram pituitary using an immunoperoxidase technique applied to semithin serial sections and compared with that of some of the hormones of the anterior pituitary. Chromogranin-immunoreactivity was found in gonadotrophs (all three), thyrotrophs (A with some positive for C) and corticotrophs (a fraction with A and fewer with B and C). The mammotrophs and somatotrophs were negative. Chromogranin C was the only one of the three to be located in the pars nervosa, whilst chromogranin B was rarely found in the pars intermedia. The results suggest that chromogranins A, B and C are not always stored together, some hormone-containing cells do not contain immunohistologically detectable levels of the chromogranins.