ABSTRACTThis study attempted to clarify the role of endothelin A and B (ETAand ETB) receptors in modulating aqueous humor dynamics in the rabbit eye. Intraocular pressure (IOP), aqueous flow, total outflow facility, and uveoscleral outflow were measured before, and 24 hours after, intravitreal injection (20 μl) of a selective ETBagonist, sarafotoxin S6c (SRTX S6c, 10-5M), into one eye and its vehicle into the contralateral eye. The measurements were also performed before and after injection of a selective ETA antagonist, 97-139 (10−2M) + ET-1 (10−5M) into one eye, and vehicle + ET-1 (10−5M) into the contralateral eye. In the SRTX S6c-treated eye, total outflow facility increased significantly by 106% compared with that in the vehicle-treated eye 24 hours after injection; aqueous flow and uveoscleral outflow failed to change significantly. The ETAantagonist 97-139 inhibited the decrease in aqueous flow partially, but significantly, but failed to inhibit the increase in total outflow facility caused by ET-1. Therefore, both ETAand ETBplay a significant role in modulating aqueous humor dynamics in the rabbit eye. ETAcan modulate aqueous humor production, at least in part. ETBcan modulate total outflow facility, and the possibility for ETBin modulating aqueous humor formation cannot be rul
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