Presence of Renin, Angiotensinogen, and Converting Enzyme in Human Pituitary Lactotroph Cells and Prolactin Adenomas

Abstract

Renin, angiotensinogen, and converting enzyme were detected in 10 normal human pituitary glands by immu-nohistochemical techniques. Renin was stained by polyclonal and monoclonal antibodies directed against human renih, and an antibody directed against the renin prosegment revealed the presence of prorenin. Immunoreactive angiotensinogen and an-giotensin I-converting enzyme were found in the same cells as renin. Using serial sections and double immunohistochemical labelingwith a PRL antiserum, all of the proteins of the renin-angiotensin system appeared to be localizedwithin the lacto-troph cells, and no component of the renin system was detected in any of the other pituitary cells. Renin, angiotensinogen, and angiotensin I-converting enzyme also were found in 6 PRL-secreting adenomas as well as in a mixed PRL/GH-secreting adenoma. The renin content of a PRL adenoma was about 1/100th that of a normal kidney. Renin activity could be blocked by an anticatalytic human renin antibody. No renin, angiotensinogen, or angiotensin I-converting enzyme wasfound in 6 GH-secreting adenomas, 1 corticotroph adenoma, or 10 nonsecreting pituitary adenomas. Thecolocalization of proteins of the reninangiotensin system suggests production of angiotensin II within the lactotroph cells and favors the hypothesis of a paracrine action of this peptide.