Medow M S, Roth K S, Goldmann D R, Ginkinger K, Hsu B Y, Segal S
Proc Natl Acad Sci U S A. 1986 Oct;83(19):7561-4. doi: 10.1073/pnas.83.19.7561.
Proline uptake by rat renal brush border membrane vesicles from animals 7 days of age and older has been examined to delineate developmental changes in membrane function that may underlie the physiological hyperprolinuria of young animals. Although the two proline transport systems normally present in adult membranes were found in membranes from young animals, the proline "overshoot" resulting from a sodium ion gradient is minimal and increases with age of the animal from which the membranes were isolated. This is associated with a severalfold faster entry of 22Na into vesicles of the 7-day-old animal compared to entry into membranes prepared from adult kidneys. The very rapid dissipation of the sodium gradient thus diminishing the driving force for transmembrane proline movement may explain the changes in proline overshoot observed in membranes from young animals. The altered sodium permeability is consistent with the fact that young animals have a generalized inability to reabsorb other amino acids whose transport is known to be sodium gradient stimulated.
对7日龄及以上大鼠肾刷状缘膜囊泡的脯氨酸摄取进行了研究，以阐明膜功能的发育变化，这些变化可能是幼龄动物生理性高脯氨酸尿症的基础。尽管在成年膜中正常存在的两种脯氨酸转运系统也存在于幼龄动物的膜中，但由钠离子梯度导致的脯氨酸“过冲”现象很轻微，且随着分离膜的动物年龄增长而增加。这与7日龄动物的囊泡中22Na进入速度比成年肾脏制备的膜快几倍有关。钠离子梯度的迅速消散从而降低了跨膜脯氨酸移动的驱动力，这可能解释了在幼龄动物膜中观察到的脯氨酸过冲变化。钠通透性的改变与幼龄动物普遍无法重吸收其他已知其转运受钠梯度刺激的氨基酸这一事实相符。
