HIGH-LEVELS OF HUMAN CHYMASE EXPRESSION IN THE PINEAL AND PITUITARY-GLANDS

The brain renin-angiotensin system plays a role in both cardiovascular homeostasis and neurosecretory functions. Since the mechanisms of ang iotensin (Ang) II formation in the human brain have not been clarified , the aims of the present study were to determine the presence of huma n chymase and angiotensin I-converting enzyme (ACE) in human and non-h uman brains. In the human brain, the total Ang II-forming activity was significantly higher in the pineal and pituitary glands than those in other regions. In other species (rat, bovine and porcine), the level of chymase as well as total Ang II-forming activities in pineal glands were significantly lower than those in human glands. High levels of c hymase-like immunoreactivity (ir) were found in the arteriolar endothe lial cells, adventitial mesenchymal cells and in parenchymal cells of the human pineal and pituitary glands while ACE-ir was mostly observed in the endothelial cells and occasionally found in parenchymal cells. Our study provides the first evidence that human chymase exists in th e pineal and pituitary glands. The remarkable regional and species dif ferences in mechanisms of Ang II formation suggest a specific role of chymase or ACE in the human brain. (C) 1997 Elsevier Science B.V.