Abstract
Abstract: :
Purpose: It has been demonstrated that the isolated bovine ciliary epithelium transports Cl into the aqueous humor (AH) side (1) and that the in vivo [Cl] in AH is higher than in plasma (PL) (2). More recent studies show that the isolated pig ciliary body also transports Cl from the blood side into the aqueous side (3) and thus it may constitute a driving force for fluid secretion. Therefore, porcine AH may also exhibit a higher [Cl] than PL; consequently the concentrations of Cl, Na and K were measured in AH and PL samples from this animal. Samples were also taken from sheep for comparison. Methods: Blood and AH were obtained from pigs and sheep when the animals were unconscious before being sacrificed following the standard procedure of the slaughterhouse in Corrientes, Argentina. Electrolyte concentrations were determined by a Nova Electrolyte Analyzer (Nova Biomedical). Results: Samples of AH from 18 pig eyes (9 pigs) gave values of 107.6±1.4, 131.9±0.9, and 3.6±0.1 mM for Cl, Na and K respectively. There was no statistically significant difference between the measured values of the two eyes. The PL values of the 9 pigs were 101.9±1.0, 140.2±0.9, and 4.9±0.2 mM for Cl, Na and K respectively. Cl, in AH was significantly higher than in PL by about 5.7 mM, p<0.01 as paired data. [Na] and [K] were significantly lower in AH than in PL. Similarly to pigs, the AH/PL of 11 sheep were 123.9±0.9/108.6±1.0, 138.6±0.5/143.9±0.5, and 4.2±0.1/4.4±0.2 for the Cl, Na and K concentrations respectively. The differences in Cl and Na concentrations between AH and PL were statistically significant, p< 0.01. Conclusion: The higher Cl concentration in AH than in PL that we report is consistent with an active Cl transport in the blood–to–aqueous direction as described in bovine and pig. Given the AH/PL Cl concentration ratio >1 in sheep, an active Cl transport is also presumed in this animal. Thus, the ciliary epithelium of any of these 3 species may be an adequate model for the ionic transport mechanism in human, which shows a AH/PL [Cl] larger than one. 1. Do CW, To CH. Chloride secretion by bovine ciliary epithelium: a model of aqueous humor formation. IOVS. 2000; 41:1853–60. 2. Gerometta R et al. Chloride concentration in bovine aqueous humor is higher than in plasma. IOVS. 2003; ARVO E–Abstract 3444. 3. Kong MCW, To CH. Chloride secretion by porcine ciliary body epithelium. IOVS. 2003; ARVO E–Abstract 3428.
Keywords: aqueous • anterior chamber • ciliary body