Angiotensin(1-7) and ACE2, "The Hot Spots" of Renin-Angiotensin System, Detected in the Human Aqueous Humor

Abstract

Background: The main purpose of the study was to establish whether essential components of the renin-angiotensin system (RAS) exist in the human aqueous humor.

Methods: Forty-five patients ≥ 60 (74±7) years of age undergoing cataract surgery at Tampere University Hospital were randomly selected for the prospective study. The exclusion criterion was the use of oral antihypertensive medicine acting via renin-angiotensin system. Aqueous humor samples were taken at the beginning of normal cataract extraction. The samples were frozen and stored at -80 °C. The concentrations of intraocular endogenous RAS components Ang(1-7), ACE2, and ACE1 were measured using ELISA.

Results: Concentration medians of Ang(1-7), ACE2, and ACE1 in the aqueous humor were: Ang(1-7) 4.08 ng/ml, ACE2 2.32 ng/ml and ACE1 0.35 ng/ml. The concentrations were significantly higher in glaucomatous than in non-glaucomatous eyes, ACE1 (p=0.014) and Ang(1-7) (p=0.026) vs non-glaucomatous eyes.

Conclusions: Ang(1-7), ACE2 and ACE1 are found in the human aqueous humor. The observations are consistent with the conception that local tissue-RAS exists in the human eye and it might have a role in the control of intraocular pressure.

Keywords: Angiotensin (1-7); angiotensin II; angiotensin converting enzyme 1; angiotensin converting enzyme 2; aqueous humor; glaucoma; renin-angiotensin system.

Fig. (1)

Individual aqueous humor concentrations of Ang(1-7), ACE2 and ACE1 in non-glaucomatous (white open circles) and glaucomatous (black spots) patients. Comparison with Mann-Whitney test, *p<0.05. Patients using ACE inhibitors (plus marks) or ATreceptor blockers (x marks) are also shown; these patients were excluded from the data in determination of the median concentrations (horizontal lines). For abbreviations see Table 1.