Fulceri R, Romani A, Pompella A, Benedetti A
Istituto di Patologia Generale dell'Università di Siena, Italy.
Biochim Biophys Acta. 1990 Feb 16;1022(1):129-33. doi: 10.1016/0005-2736(90)90409-h.
(1) The features of MgATP-dependent Ca2+ accumulation under stimulation with glucose 6-phosphate were studied in rat kidney microsomes. (2) Ca2+ accumulated in the presence of MgATP alone does not exceed approx. 2 nmol/mg protein. (3) Glucose 6-phosphate markedly stimulates Ca2+ accumulation, up to steady-state levels approx. 15-fold higher than in its absence. (4) The hydrolysis of glucose 6-phosphate by glucose-6-phosphatase is essential for the stimulation, as shown by inhibiting the glucose 6-phosphate hydrolysis with adequate concentrations of vanadate. Inorganic phosphate is accumulated in microsomal vesicles during glucose 6-phosphate-stimulated Ca2+ uptake in equimolar amounts with respects to Ca2+. (5) Increasing concentrations of glucose 6-phosphate result in increasing stimulations of Ca2+ uptake, until a maximal Ca2(+)-loading capacity of approx. 27 nmol/mg microsomal protein is reached. It is suggested that the enlargement of the kidney microsomal Ca2+ pool induced by glucose 6-phosphate (an important metabolite in kidney) might play a role in the regulation of Ca2+ homeostasis in kidney tubular cells.
(1) 在大鼠肾脏微粒体中研究了6-磷酸葡萄糖刺激下MgATP依赖的Ca2+积累的特征。(2) 仅在MgATP存在下积累的Ca2+不超过约2 nmol/mg蛋白质。(3) 6-磷酸葡萄糖显著刺激Ca2+积累，达到比无6-磷酸葡萄糖时高约15倍的稳态水平。(4) 如用适当浓度的钒酸盐抑制6-磷酸葡萄糖水解所显示，6-磷酸葡萄糖磷酸酶对6-磷酸葡萄糖的水解对于这种刺激至关重要。在6-磷酸葡萄糖刺激的Ca2+摄取过程中，无机磷酸盐以与Ca2+等摩尔的量积累在微粒体小泡中。(5) 6-磷酸葡萄糖浓度增加导致Ca2+摄取刺激增加，直至达到约27 nmol/mg微粒体蛋白质的最大Ca2+装载能力。有人提出，6-磷酸葡萄糖（肾脏中的一种重要代谢物）诱导的肾脏微粒体Ca2+池扩大可能在肾小管细胞Ca2+稳态调节中起作用。
