Distribution Of Angiotensin (1–7) In The Retina.

Abstract

Abstract: : Purpose: To evaluate the distribution and content of angiotensin (1–7) in the porcine retina in the presence and absence of ischemia. Methods: Left and right eyes were harvested 14 days after unilateral carotid artery ligation surgery. The animals were undergoing surgery for evaluating cGMP regulation in the heart. Carotid artery ligation increases blood pressure via reflex action of the arterial baroreceptors and the plasma and tissue angiotensin systems may be activated. The eyes from the ligated side and the opposite (control) side were fixed in 4% paraformaldehyde in 0.1M phosphate buffer, cryoprotected with 21% sucrose and embedded using OCT Tissue Tek. For angiotensin (1–7) localization, 10 µm frozen sections were blocked with 5% BSA and incubated with the anti–angiotensin (1–7) rabbit antibody (1:200) produced in–house. After an overnight incubation at 40 C, sections were rinsed with PBS. After 1h of incubation with the secondary antibody (conjugated to Texas Red) sections were rinsed with PBS, mounted and observed under the fluorescence microscope and the images digitally recorded. Results: Angiotensin (1–7) was localized to the nerve fiber layer. Carotid artery ligation produced a significant reduction in the immunohistochemical staining of angiotensin (1–7). Angiotensin(1–7) is considered to be the vasodepressor analogue of the renin–angiotensin system. The altered distribution of angiotensin (1–7) may be due to the upregulation of the renin–angiotensin system; the vasoconstrictor pathway in preference to the vasodialator pathway or a loss of cells producing angiotensin (1–7). Conclusions: Angiotensin (1–7) is present in the retina. The response to carotid artery ligation suggests that retinal angiotensin (1–7) is labile and amenable to a systemic circulatory stimulus. In addition, our study also indicates that a systemic circulatory insult such as internal carotid intima medial wall thickening and plaque may have neurovascular consequences for the retina.

Keywords: blood supply • ischemia • retina