Initial observations of rabbit retinal pigment epithelium-choroid-sclera preparations

Retinal pigment epithelium (RPE)-choroid-sclera preparations from black dutch-belted rabbits were sealed in an Ussing chamber maintained at 37-39 degrees C. Typical preparations produced a spontaneous voltage (Ve) of 12.5 mV (retina side positive) and possessed an electrical resistance (R) of 350 ohm-cm2. Both of these values can be attributed to the RPE. Ouabain and amiloride diminished the Ve without affecting R. Ouabain was effective when applied to the apical but not to the basolateral side of the preparation, suggesting the presence of a Na-K ATPase on rabbit RPE apical membrane similar to that found in bullfrogs, embryonic chickens, cats and dogs. Dinitrophenol also reduced Ve. Digoxin, furosemide, bumetanide, ethacrynic acid and chlorothiazide had no apparent effect upon Ve and R. The lack of response to furosemide, bumetanide and ethacrynic acid strongly suggests that, unlike RPE from other species, rabbit RPE does not possess Na-dependent Cl transport and/or does not possess furosemide receptors on its apical membrane.