Pretorius H T, Kastin A J, Banks W A
Brain Res Bull. 1986 Dec;17(6):829-31. doi: 10.1016/0361-9230(86)90095-x.
Tyr-MIF-1 (Tyr-Pro-Leu-Gly-amide) and the enkephalins have previously been shown with in vivo studies to be transported out of the brain by a saturable, carrier-mediated system. The possibility that this transport system occurs at the level of the endothelial cells was tested by measuring the ability of isolated brain capillaries to bind radioiodinated Tyr-MIF-1. The binding of labeled Tyr-MIF-1 was displaced by unlabeled Tyr-MIF-1 (50% inhibition at 1.5 X 10(-6) M) and by nonradioactive (I127) iodinated Tyr-MIF-1, but not by tyrosine, MIF-1 (Pro-Leu-Gly-amide), Tyr-Pro, or D-Tyr-MIF-1. This pattern of inhibition is similar to that found for the in vivo transport of Tyr-MIF-1 out of the brain. Tyr-MIF-1 did not appear to be bound by albumin or degraded by cells aged 3-7 days at 4 degrees C. These results suggest that the transport system previously described in vivo for Tyr-MIF-1 and the enkephalins may be associated with the brain endothelial cells.
酪氨酰-促黑素细胞激素释放抑制因子-1（酪氨酰-脯氨酰-亮氨酰-甘氨酰胺）和脑啡肽先前的体内研究表明，它们可通过一种可饱和的、载体介导的系统转运出脑。通过测量分离的脑毛细血管结合放射性碘化酪氨酰-促黑素细胞激素释放抑制因子-1的能力，来测试这种转运系统是否在内皮细胞水平发生。未标记的酪氨酰-促黑素细胞激素释放抑制因子-1（在1.5×10⁻⁶ M时50%抑制）和非放射性（¹²⁷I）碘化酪氨酰-促黑素细胞激素释放抑制因子-1可取代标记的酪氨酰-促黑素细胞激素释放抑制因子-1的结合，但酪氨酸、促黑素细胞激素释放抑制因子-1（脯氨酰-亮氨酰-甘氨酰胺）、酪氨酰-脯氨酸或D-酪氨酰-促黑素细胞激素释放抑制因子-1则不能。这种抑制模式与酪氨酰-促黑素细胞激素释放抑制因子-1在体内转运出脑的情况相似。酪氨酰-促黑素细胞激素释放抑制因子-1似乎未与白蛋白结合，也未在4℃下被培养3 - 7天的细胞降解。这些结果表明，先前在体内描述的酪氨酰-促黑素细胞激素释放抑制因子-1和脑啡肽的转运系统可能与脑内皮细胞有关。
