INITIAL OBSERVATIONS ON ISOLATED RETINAL-PIGMENT EPITHELIUM-CHOROID OF CAT

  • 1 January 1978
    • journal article
    • research article
    • Vol. 17  (7) , 675-678
Abstract
An in vitro preparation of a mammalian retinal pigment epithelium (RPE)-choroid was developed, that of the cat, to study the RPE in isolation from the neural retina. The purpose of these initial experiments was to evaluate the electrical characteristics of the tissue and the ionic properties of the RPE apical membrane. They were designed so that the results would be directly comparable to those previously obtained on a more extensively studied cold-blooded preparation, the bullfrog. The electrical characteristics of the best cat tissues were similar to those routinely obtained in bullfrog; the average cat apical membrane potential was 20 mV more depolarized than that of frog. The apical membrane of cat resembled the frog''s in having a large sensitivity to K+, but it had a relatively smaller sensitivity to HCO3- and a relatively larger sensitivity to Na+. The cat, like the frog, also had a ouabain-sensitive mechanism on its apical membrane that directly contributed to membrane potential. Two factors contributing to the lower apical membrane potential in cat were the higher K+ concentration of the mammalian salt solution and the Na+ conductance of the apical membrane.

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