McNamara P D, Rea C T, Segal S
Division of Biochemical Development and Molecular Diseases, Children's Hospital of Philadelphia, PA 19104-4399.
Biochim Biophys Acta. 1992 Jan 10;1103(1):101-8. doi: 10.1016/0005-2736(92)90062-q.
The shared transport system for uptake of L-cystine and L-lysine was examined in isolated rat renal brush-border membrane vesicles for the ionic requirements for activation of the system. No requirement for sodium was seen for either cystine or lysine influx. However, the efflux of lysine from the vesicle was stimulated by Na+. Therefore, the transport system appears to be asymmetric in its requirement for sodium. Two different divalent cations were used in the membrane isolations which resulted in different responses of cystine uptake to the electrogenic movement of K+ out of the vesicle. Membranes prepared by Mg-aggregation showed no stimulation of cystine influx by the imposition of a transient interior negative potential while vesicles prepared by Ca-aggregation did respond to electrogenic stimulation by an outwardly directed K-diffusion potential in the presence of valinomycin. Lysine influx was stimulated by electrogenic potassium efflux in both Mg-prepared and Ca-prepared membranes. No difference in sodium requirement for cystine influx was seen between the vesicles isolated by different cation-aggregation methods.
在分离出的大鼠肾刷状缘膜囊泡中，研究了L-胱氨酸和L-赖氨酸摄取的共享转运系统，以了解激活该系统所需的离子条件。胱氨酸或赖氨酸内流均未见对钠的需求。然而，钠会刺激赖氨酸从囊泡中流出。因此，该转运系统对钠的需求似乎是不对称的。在膜分离过程中使用了两种不同的二价阳离子，这导致胱氨酸摄取对钾离子从囊泡中电致性外流的反应不同。通过镁聚集制备的膜在施加瞬时内向负电位时，胱氨酸内流未受刺激，而通过钙聚集制备的囊泡在缬氨霉素存在下，确实会对由外向钾扩散电位引起的电刺激作出反应。在镁制备的膜和钙制备的膜中，电致性钾外流均刺激了赖氨酸内流。不同阳离子聚集方法分离出的囊泡在胱氨酸内流对钠的需求方面未见差异。
