Mast cells in the anterior uvea of the rabbit. Intraocular effects of compound 48/80 in the rabbit.

In the present study, the presence and localization of mast cells and the intraocular effects of compound 48/80 have been studied in detail in the rabbit eye using histochemical and physiological methods. In histochemical studies mast cells were localized in the anterior uvea, especially in the ciliary and iridial processes. Intracamerally injected, compound 48/80 caused an increase in the intraocular pressure, disruption of the blood-aqueous barrier and an increase in the cAMP content in the aqueous humour. Miosis was observed only after higher doses of compound 48/80 (greater than 100 micrograms) and even then only one-half of the eyes responded. The intraocular effects, excluding miosis, of compound 48/80 resembled an on/off-type of response, where 20 micrograms caused only minor changes, if any, and 50 micrograms gave a maximal response. The ocular hypertensive reaction developed a tachyphylaxis so that the second and third consecutive dose of compound 48/80 (100 micrograms) produced no significant change in IOP. The results indicate that mast cells, which are present in the anterior uvea in an extent not known previously, might be involved in certain inflammatory reactions in the rabbit eye. The inconsistent and slight miosis after the intracameral application of compound 48/80 indicates that the mechanism is different from that caused by sensory nerve stimulation. The rapid development of tachyphylaxis after consecutive application of compound 48/80 suggests that mast cells are easily depleted which might be useful for further studies to evaluate the functional role of mast cells in different pathophysiological conditions in the rabbit eye.