Immunohistochemical Detection of Dopamine D2 Receptors in Human Pituitary Adenomas

Thirty one pituitary adenomas and 3 samples of peritumoral anterior pituitary tissue were immunostained with an antibody raised against dopamine D2 receptor protein. The positive reactions were found in cell cytoplasm, a subpopulation of cell nuclei and the intratumoral blood vessels walls. As expected, the positive immunostaining was shown in cytoplasm and/or cell nuclei of all examined prolactinomas (7/7). In acromegaly the positive D2 staining occurred in 5/7 samples, in gonadotropinomas in 6/8 and in plurihormonal adenomas 2/4. The lowest expression was observed in corticotropinomas (1/5). These findings corroborate with the well known efficacy of D2 agonists in the treatment of prolactinomas and somatotropinomas, and support the rationale of the therapeutic trials with these compounds in gonadotropinomas. Moreover, the presence of D2 receptors in intratumoral blood vessels walls constitutes the possibility of the anti-angiogenic action of D2 agonists in pituitary adenomas.