Effects of forskolin, prostaglandin f2α and ba2± on the short-circuit Current of the isolated rabbit iris-ciliary body

To gain information on the role of cyclic AMP (cAMP), ion transport and cell membrane permeability on aqueous humor formation, agents with well-known effects on transport properties in other epithelia were tested on the isolated rabbit iris-ciliary body. Forskolin stimulated the short-circuit current (SCO by 37.5? when added to the aqueous-side solution. Forskolin was ineffective when added to the blood-side solution or when HCCC was absent from the bathing solutions. The effect of forskolin confirms the presence of adenylate cyclase in the ciliary epithelium and the involvement of cAMP in ion transport. In HCOl-rich media, 5 × 10″ M prostaglandin F2_α. (PGF-_α), produced a prompt 25% increase in the SCC when added to the aqueous-side, and a small stimulatory SCC response when added to the blood-side. No change in SCC occurred when PGF_α was added to either side of a HCO₃-free bathing solution. It is implied that cAMP acts on a HCO₃ dependent transport system. These results are consistent with the previously observed stimulation of the SCC by 8Br-cAMP. Ba, 2.5 mM, on the aqueous-side increased the SCC by 240.5% but reduced the SCC by 26% when 2+ added to the blood-side solution. The Ba effects indicate the presence of high conductance K⁺ channels in the basolateral membranes of both the pigmented and non-pigmented cell layers.