Electron Probe X-Ray Microanalysis of Rabbit Ciliary Epithelium

• Published in: Experimental eye research 1996-02, Vol.62 (2), p.131-140
• Main Authors: BOWLER, JOANNE M., PEART, DAVID, PURVES, ROBERT D., CARRÉ, DAVID A., MACKNIGHT, ANTHONY D.C., CIVAN, MORTIMER M.
• Format: Article
• Language: English
• Subjects: Animals; aqueous humor secretion; Biological and medical sciences; Chloride Channels - analysis; Chlorides - analysis; Ciliary Body - chemistry; Cl -channels; Electron Probe Microanalysis; Epithelium - chemistry; Eye and associated structures. Visual pathways and centers. Vision; Fundamental and applied biological sciences. Psychology; gluconate; intracellular ionic concentrations; Male; Na,K-exchange pump; Nitrates - pharmacokinetics; NO 3; non-pigmented cells; Phosphorus - analysis; pigmented cells; Potassium - analysis; Rabbits; Sodium - analysis; Sulfur - analysis; Vertebrates: nervous system and sense organs; Water - analysis
• ISSN: 0014-4835; 1096-0007
• DOI: 10.1006/exer.1996.0017

Rabbit iris–ciliary bodies were preincubated in control and experimental Ringer's solutions before quick freezing, cryosectioning, dehydration and electron probe X-ray microanalysis. After preincubation in a baseline bicarbonate-free Cl -Ringer's solution, the ciliary epithelial intracellular Na +, K +and Cl -concentrations were estimated to be 15±3, 162±14 and 46±5mmolkg -1intracellular water, respectively. The water and elemental Na, K, Cl and P contents were similar in the non-pigmented (NPE) and pigmented (PE) ciliary epithelial cells. As expected, inhibition of the Na,K-exchange pump by preincubation with ouabain markedly increased the intracellular Na content, and markedly reduced the intracellular K content, verifying the validity of the experimental analysis. The Cl -channels of the NPE cells likely play a critical role in determining the rate of aqueous humor formation. Therefore, we have examined the effects of altering Cl -transport on the intracellular composition in this initial microprobe study of the ciliary epithelium. As expected, exposure to bicarbonate increased the intracellular Cl and water contents. Replacement of external Cl -by NO 3 -was twice as effective as replacement by gluconate in leaching Cl -out of the intracellular compartment. An unexpected finding was that NO 3 -replacement of internal Cl -substantially increased the intracellular Na and decreased the intracellular K content, possibly by stabilizing the Na,K-pump in the E 1P form and inhibiting enzyme activity.