Reinersdorff D V, Bush E, Liberato D J
Department of Vitamin and Nutrition Research, F. Hoffmann-La Roche LTD, Basel, Switzerland.
J Lipid Res. 1996 Sep;37(9):1875-85.
The kinetics of vitamin A and its major metabolites were investigated in humans. Eleven healthy male subjects ingested 105 mumol (100,000 IU) of [8,9,19-13C]retinyl palmitate in an oily solution. Twenty-seven blood samples were collected during the 1-week study. Plasma samples were analyzed for retinyl esters and for [12C]- and [8,9,19-13C]retinol. Retinol isotopes were quantified using a newly developed GC-MS method. Total retinyl esters peaked at about 4.45 mumol/L from 3.5 to 12 h after dosing. As a result of the perturbation of the tracee system, the plasma concentration of [12C]retinol increased and then decreased as the concentration of [8,9,19-13C]retinol increased, indicating rapid distribution kinetics. A broad single peak (1.16 +/- 0.32 mumol/L) was observed for [8,9,19-13C]retinol at about 10 to 24 h postdose; this likely reflects hepatic secretion of [8,9,19-13C]retinol associated with retinol-binding protein. Then, declining levels of the tracer and increasing levels of the tracee were observed. At its peak, the ingested [8,9,19-13C]retinol reached about 51% of the observed total plasma retinol concentration. This percentage dropped to 13.4% on day 7 indicating slow final elimination from plasma. Our data support the concept that the liver follows the principle "last in/first out' in maintaining vitamin A homeostasis.
对人体中维生素A及其主要代谢产物的动力学进行了研究。11名健康男性受试者摄入了105微摩尔（100,000国际单位）溶解于油溶液中的[8,9,19-¹³C]视黄醇棕榈酸酯。在为期1周的研究期间采集了27份血样。分析血浆样本中的视黄醇酯以及[¹²C]-和[8,9,19-¹³C]视黄醇。使用新开发的气相色谱-质谱法对视黄醇同位素进行定量。给药后3.5至12小时，总视黄醇酯浓度峰值约为4.45微摩尔/升。由于示踪系统受到干扰，随着[8,9,19-¹³C]视黄醇浓度的增加，[¹²C]视黄醇的血浆浓度先升高后降低，表明分布动力学迅速。给药后约10至24小时观察到[8,9,19-¹³C]视黄醇出现一个宽单峰（1.16±0.32微摩尔/升）；这可能反映了与视黄醇结合蛋白相关的[8,9,19-¹³C]视黄醇的肝脏分泌。然后，观察到示踪剂水平下降和被追踪物水平上升。在峰值时，摄入的[8,9,19-¹³C]视黄醇达到观察到的总血浆视黄醇浓度的约51%。该百分比在第7天降至13.4%，表明从血浆中最终清除缓慢。我们的数据支持肝脏在维持维生素A稳态时遵循“后进先出”原则这一概念。
