Biochemical and immunohistochemical localization of renin in human pituitary

The renin content of human pituitaries obtained at autopsy of eight patients (four males and four females) within 3 hours after death from various diseases was determined. The pituitaries contained a significant amount of renin (5.5 +/- 1.6 mg of angiotensin I/mg of protein/hour). Although much less (1/1000) than that in human kidneys (4.5 micrograms of angiotensin I/mg of protein/hour), this content was about 10 times higher than that in normal plasma (0.5 ng of angiotensin I/mg of protein/hour). More than 50% of the renin activity was inhibited by antihuman renin antibody. These results are the first detection of a significant amount of renin in the human pituitary. No difference in pituitary renin content between males and females was detected; the pituitaries from the two youngest patients showed the highest levels. Immunohistochemical staining showed no positive cells in the intermediate and posterior lobes and many positive cells in the anterior lobe. Serial sections were examined, and renin-containing cells were immunohistochemically identified as polactin-producing cells without distinction as to the sex of the donor. This demonstration of the intracellular presence of immunoreactive renin lends strong support to the idea that renin is not a contaminant of pituitary preparations due to entrapped plasma, but is endogenous to the human pituitary.