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LAWRENCE A. COBEN, EDWARD COTLIER, CLAUDIA BEATY, BERNARD BECKER; Proline Transport by Rabbit Ciliary Body-Iris in Vitro. Invest. Ophthalmol. Vis. Sci. 1970;9(12):949-958.
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The rabbit ciliary body-iris preparation in vitro shows concentrative uptake of 14C-proline which is resistant to anoxia and to cyanide; inhibited by ouabain; and abolished in the absence of external sodium or by cold (0° C). It has a Q10 (27 to 37° C.) of 1.7. Uptake is decreased by preloading with unlabeled proline. Exchange diffusion of the accelerative type is demonstrable during efflux of 14C-proline. Inhibitory effects of other neutral amino acids in this tissue differ from effects in rabbit choroid plexus and optic nerve. In the ciliary body-iris preparation the neutral amino acids do not divide themselves into a high-affinity group, the imino acids, and a group with lesser affinity. Neither arginine nor aspartic acid inhibits the uptake of 14C-proline. Saturable proline uptake is nearly completely inhibited by 50 mM N-methylalanine. Thus, proline is concentrated in the ciliary body-iris preparation by a mobile carrier system largely of the Ehrlich cell A type. Alanine uptake is only partly inhibited by N-methylalanine, and the residual saturable uptake is only partly sodium dependent. The ciliary body-iris preparation, therefore, transports alanine by three carrier systems like those described in the Ehrlich cell as the A, the ASC, and the L mediations. The functional role of these carrier systems is discussed.
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