Activities of Angiotensin-Converting Enzymes ACE1 and ACE2 and Inhibition by Bioactive Peptides in Porcine Ocular Tissues

Purpose: An active local renin-angiotensin system (RAS) has recently been found in the human eye. The aim of the present study was to compare the activities of central RAS enzymes (ACE1 and 2) in porcine ocular tissues, morphologically and physiologically close to the human eye. In addition, the effects of three ACE-inhibitory tripeptides on these enzymes were evaluated.Methods: Enucleated fresh porcine eyes were used. Activities of ACE1 and ACE2 and their inhibition by bioactive tripeptides (Ile-Pro-Pro, Val-Pro-Pro, Leu-Pro-Pro) as well as by a standard ACE-inhibitor captopril were assayed in the vitreous body, the retina and the ciliary body using fluorometric detection methods.Results: Activity of ACE1 as well as ACE2 was found in all tissues evaluated. ACE1 activity was markedly higher in the ciliary body (3.7 ± 0.7 mU/mg protein) than in retina (0.2 ± 0.02 mU/mg), whereas ACE2 activities in the ciliary body (0.2 ± 0.02 mU/mg) and retina (0.2 ± 0.01 mU/mg) were at the same level. In the vitreous body...