Choy Camus, Benzie Iris, Cho Pauline
Department of Optometry and Radiography, The Hong Kong Polytechnic University, Hong Kong SAR, Kowloon, China.
Curr Eye Res. 2003 Jul;27(1):55-60. doi: 10.1076/ceyr.27.2.55.15458.
To investigate inter-relationships between total antioxidant capacity and ascorbate concentration in plasma and tears, and the effect of antioxidant supplementation with reference to these variables.
Twenty-one subjects were studied in this placebo-controlled, cross-over intervention trial. Fasting plasma and tear ascorbate concentrations and total antioxidant capacity (as Ferric Reducing/Antioxidant Power (FRAP)) were measured pre- and post-supplementation with vitamin C (1 g/day).
Mean +/- SD ascorbate in tears and plasma at entry were 17 +/- 6 and 52 +/- 13 micro M, respectively; FRAP values were, respectively, 273 +/- 94 and 1101 +/- 168 micro M. There was no significant correlation between tear and plasma levels (r = -0.068; P = 0.771 for ascorbate; r = 0.418; P = 0.059 for FRAP). Neither was significant correlation seen between the two variables in plasma (r = 0.162; P = 0.483) or tears (r = 0.353; P = 0.117). Acute responses (up to 3 hours) showed a similar pattern of increase in both fluids, however, peak response in tears (33 +/- 4 micro M) was much smaller and slightly later than in plasma (125 +/- 13 micro M). After 4 weeks' supplementation, ascorbate increased (P < 0.001) in both fluids, however, the increase in tear ascorbate was small (5 micro M), compared to plasma (38 micro M). The increase in tear ascorbate appeared to plateau after 2 days' supplementation; plasma levels were still increasing. Higher tear ascorbate at entry was associated (P < 0.05) with smaller supplementation-related response. No significant changes in FRAP were seen in either fluid (P > 0.05).
Ascorbate concentration in both plasma and tears increased with vitamin C supplementation, but the total antioxidant capacity of these fluids did not. Furthermore, the increase in tear ascorbate was modest in comparison to that in plasma, and is suggestive of a "ceiling" for tear ascorbate of under 40 micro M. Results support the concept of a control mechanism for an integrated antioxidant defense system, and suggest that the amount of ascorbate in tears is both actively controlled and purposefully limited.
研究血浆和泪液中总抗氧化能力与抗坏血酸浓度之间的相互关系，以及抗氧化剂补充对这些变量的影响。
在这项安慰剂对照的交叉干预试验中对21名受试者进行了研究。在补充维生素C（1克/天）前后，测量空腹血浆和泪液中的抗坏血酸浓度以及总抗氧化能力（以铁还原/抗氧化能力（FRAP）表示）。
入组时泪液和血浆中抗坏血酸的均值±标准差分别为17±6和52±13微摩尔；FRAP值分别为273±94和1101±168微摩尔。泪液和血浆水平之间无显著相关性（抗坏血酸：r = -0.068；P = 0.771；FRAP：r = 0.418；P = 0.059）。血浆（r = 0.162；P = 0.483）或泪液（r = 0.353；P = 0.117）中的这两个变量之间也无显著相关性。急性反应（长达3小时）显示两种液体中均有类似的升高模式，然而，泪液中的峰值反应（33±4微摩尔）比血浆中的峰值反应（125±13微摩尔）小得多且略晚。补充4周后，两种液体中的抗坏血酸均升高（P < 0.001），然而，与血浆中抗坏血酸升高38微摩尔相比，泪液中抗坏血酸升高幅度较小（5微摩尔）。补充2天后泪液中抗坏血酸的升高似乎趋于平稳；血浆水平仍在升高。入组时泪液中抗坏血酸水平较高与补充相关的反应较小有关（P < 0.05）。两种液体中FRAP均无显著变化（P > 0.05）。
补充维生素C后血浆和泪液中的抗坏血酸浓度均升高，但这些液体的总抗氧化能力未升高。此外，泪液中抗坏血酸的升高幅度与血浆相比适度，提示泪液中抗坏血酸的“上限”低于40微摩尔。结果支持综合抗氧化防御系统控制机制的概念，并表明泪液中抗坏血酸的量受到主动控制且有意限制。
