Immunohistochemical detection of angiotensin receptors ATI and AT2 in normal rat pituitary gland, estrogen-induced rat pituitary tumor and human pituitary adenomas

摘要

Male rat pituitary glands, diethylstilbestrol (DES)-induced rat pituitary tumors and 12 human pituitary adenomas were immunostained with antibodies raised against ATI and AT2 angiotensin receptor proteins Positive immunostaining of ATI was observed in a subpopulation of anterior and intermediate pituitary lobe cells as well as in some nerve endings of the neurohypophysis. In the DES-induced rat pituiary tumors, the subpopulation of ATl-immunnopositive cells was smaller than in the non-tumoral anterior pituitary In human pituitary adenomas, weak ATI immunostaining was found in 5 tumors. In the remaining adenomas, the ATI immunostaining was trace (doubtful) or absent. The ATI immunostaining in the peritumoral non-neoplastic pituitary tissue was stronger than that observed in the tumors The normal rat pituitaries and rat tumors did not show immunostaining with anti-AT2 antibody. In human pituitary adenomas, the tumoral cells were AT2- negative but moderate to strong AT2 immunostaining was observed in intratumoral blood vessel walls. The data suggest that the experimental (in rat) and spontaneous (in man) pituitary tumorigenesis is associated with the down-regulation of ATI receptors. The expression of AT2 receptors, in turn, may be connected with the process of tumoral neo-angiogenesis