The effect of theophylline on the breakdown of the blood-aqueous barrier in the rabbit eye.

A disruption of the blood-aqueous barrier in rabbit eyes was elicited by topical prostaglandin E2, infrared irradiation of the iris, or subcutaneous alpha-melanocyte stimulating hormone (alpha-MSH). The course of the inflammatory reaction was followed by photoelectrical measurements of the aqueous flare in the anterior chamber. Pretreatment with intravenous theophylline, a phosphodiesterase inhibitor, significantly increased the protein leakage caused by prostaglandin E2 and alpha-MSH, but the response to infrared irradiation was slightly but not significantly enhanced. Intravenous theophylline given in higher doses caused per se an aqueous flare increase, which could not be inhibited by pretreatment with topical indomethacin. Our results indirectly indicate that accumulation of intraocular cAMP promotes a barrier damage and that cAMP might be the common effector of the barrier breakdown caused by prostaglandin as well as by nonprostaglandin agents.