Effects of forskolin, prostaglandin F2 alpha, 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 (SCC) by 37.5% when added to the aqueous-side solution. Forskolin was ineffective when added to the blood-side solution or when HCO3- 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 HCO3- -rich media, 5 X 10(-5) M prostaglandin F2 alpha (PGF2 alpha), 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 PGF2 alpha 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. BaCl2, 2.5 mM, on the aqueous-side increased the SCC by 240.5%, but reduced the SCC by 26% when added to the blood-side solution. The Ba2+ effects indicate the presence of high conductance K+ channels in the basolateral membranes of both the pigmented and non-pigmented cell layers.
Chu
T C
TC
Candia
O A
OA
Iizuka
S
S
D000818:Animals; D001464:Barium / Q000494:pharmacology*; D002924:Ciliary Body / Q000502:physiology*; D005576:Colforsin / Q000494:pharmacology*; D015237:Dinoprost; D004553:Electric Conductivity; D004594:Electrophysiology; D005260:Female; D066298:In Vitro Techniques; D007429:Intraocular Pressure / Q000187:drug effects; D007498:Iris / Q000502:physiology*; D011460:Prostaglandins F / Q000494:pharmacology*; D011817:Rabbits
D011460:Prostaglandins F; D005576:Colforsin; D001464:Barium; D015237:Dinoprost