Angiotensin II-generating system in dog and monkey ocular tissues

1. Angiotensin II (AngII) is generated locally in several tissues, including ocular tissues. Recently, it has been suggested that in addition to angiotensin-converting enzyme (ACE), an alternative AngII-generating enzyme, chymase, is present in the cardiovascular tissues of humans, monkeys and dogs and may be involved in the local production of AngII. The purpose of the present study was to determine whether chymase contributes to AngII generation in dog and monkey ocular tissues and to clarify the intraocular AngII-generating system. 2. Chymase-like and ACE activities were measured in dog and monkey ocular tissues, carotid artery, heart and lung. Their mRNA levels were quantified using the competitive reverse transcriptase-polymerase chain reaction (RT-PCR) method. 3. Chymase-like activity was detected in the anterior uveal tract, choroid and sclera in dog eyes, but not in the cornea, lens or fluid phase (vitreous body and aqueous humor). In monkey eyes, chymase-like activity was detected in the anterior uveal tract and it was higher here than in the heart. Angiotensin-converting enzyme activity was detected in the anterior uveal tract, choroid, retina, sclera and fluid phase in both dog and monkey eyes. Chymase and ACE mRNA were detected in tissues showing enzymatic activity. 4. These findings show for the first time that chymase, in addition to ACE, is expressed locally in dog and monkey ocular tissues and may be involved in local AngII generation in the eye.