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P.A. Lewis, E. Gill, M. Chisholm, D.A. Samuelson; Smooth Muscle Actin Localization in the Iridocorneal Angle of Domestic Species . Invest. Ophthalmol. Vis. Sci. 2003;44(13):653.
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Purpose:Within the past 12 years, there has been a developing body of evidence from selected species that has revealed contractile ability among cells of the iridocorneal angle (ICA). We have most recently examined the presence of contractile cells within the ICA of canine eyes including changes associated with glaucoma. To date, our knowledge of potential ICA contractility among different domestic spp is insufficient. As we explore the influence of vascular mediators on aqueous humor dynamics in the mammalian eye, it is important to understand the potential contractile capability of the ICA among different spp. Accordingly, we have examined the presence of smooth muscle actin (smA) in the ICA of the cat, chicken, cow, horse, pig, and sheep. Methods:Sagittal sections of the whole globes from 2-5 formalin-preserved eyes of each species were cut. The sections were incubated with primary antibody (mouse anti-human sm actin) overnight at 50 degrees C and treated sequentially with secondary antibody ([rabbit anti-mouse immunoglobulin]), peroxidase-labeled streptavidin, and substrate chromagen solution (AEC) and appropriate washes. Results:Labeling was observed in the ICA of each animal with distinct species variations. Overall, smA was localized within trabecular meshwork cells mostly within the corneoscleral trabecular meshwork (CSTM), especially the outer CSTM and posterior inner CSTM, as a continuation of the outer leaf of the ciliary body musculature. The porcine ICA had the least positive reaction to smA. In the chicken, smA labeling was observed between scleral ossicles in addition to the ICA. Conclusions:It was concluded that portions of the ICA of domestic species have the ability to contract, while varying in amount and location. The variations appeared to be associated in part to the interrelationship of the ICA and the ciliary body musculature. We believe the contractile elements within the ICAs of these animals facilitate the removal of aqueous humor and are likely to be influenced by vascular mediators.
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