Aqueous humor renin, angiotensin I, and angiotensin II activity in primary open-angle glaucoma

The renin-angiotensin system is involved in the pathogenesis of retinal ischemic conditions and glaucoma. Our objective was to evaluate the renin, angiotensinconverting enzyme 1, and angiotensin-converting enzyme 2 activities in aqueous humor and blood samples of patients with and without primary open-angle glaucoma.

We analyzed samples from 56 participants who underwent ocular surgeries. The patients were divided into two groups: patients with cataract alone (n=28) and patients with cataract and primary open-angle glaucoma (n=28). Venous blood (2 ml) and aqueous humor (150 µl, via paracentesis) samples were collected during phacoemulsification (cataract only) or glaucoma surgery (cataract and primary open-angle glaucoma). The serum and aqueous humor renin, angiotensin-converting enzyme 1, and angiotensin-converting enzyme 2 activities of all patients were evaluated by fluorimetric assays, and results were analyzed by using multivariate regression analysis.

Both the aqueous humor renin activity and renin activity aqueous humor/serum ratio were significantly lower in patients with cataract and primary open-angle glaucoma than in patients with cataract only [(mean ± SE): 0.018 ± 0.006 ng/ml/h vs 0.045 ± 0.009 ng/ml/h, p<0.001; 0.05 ± 0.02 vs 0.13 ± 0.05, p=0.025]. Multivariate analyses showed a significant relationship between lower aqueous humor renin activity and primary open-angle glaucoma [coefficient (±SE): -0.029 ± 0.013, p=0.026].

Our results showed that patients with primary open-angle glaucoma had lower aqueous humor renin activity. As timolol eye drops were used by most of the primary open-angle glaucoma patients, we propose that a large sample of washed-out patients should be studied in the future to discriminate the involvement of b-blocker treatment in the aqueous humor renin activity.