An acute ocular inflammatory reaction induced by intravitreal bovine serum albumin in presensitized rabbits: the effect of phentolamine.

An acute inflammatory reaction in the uvea was challenged by an intravitreal injection of bovine serum albumin (BSA) in presensitized rabbits. During the observation time of 3 h, intraocular pressure (IOP) increased, anterior uveal blood vessels were dilated, miosis was produced, and as a sign of the breakdown of the blood aqueous barrier, protein content in the aqueous humour was increased. In the contralateral eye, the reaction consisted of an increase in IOP and a disruption of the blood aqueous barrier. As an evidence of the immunological mechanism of this acute reaction, presensitized animals intravitreally injected with saline or unimmunized rabbits which were injected with BSA showed no significant changes in IOP, pupillary diameter or protein content in aqueous humour. Phentolamine significantly reduced protein leakage into the anterior chamber of the experimental eye. It also significantly inhibited the increase in IOP and protein leakage in the contralateral eye. The present findings demonstrate that a hypertensive inflammatory phase is present in the acute experimental uveitis. The mechanisms of the reaction and the mode of action of phentolamine are discussed.