Pastuszko A, Wilson D F, Erecińska M, Silver I A
J Neurochem. 1981 Jan;36(1):116-23. doi: 10.1111/j.1471-4159.1981.tb02385.x.
Synaptosomes isolated on isosmotic Ficoll density gradients are an effective model for some aspects of neuronal function. They maintain metabolic energy levels ([ATP]/[ADP] [Pi]) and transplasma membrane electrical potentials very similar to those of neurons in the intact brain. The concentration of K+ in the external medium (K+-sensitive electrode), O2 uptake, and cytochrome c reduction (550 nm minus 540 nm) were simultaneously monitored in synaptosomal suspensions. Oxidative metabolism is the primary source of intrasynaptosomal ATP and at pH 7.4 anaerobiosis results in K+ leakage at 4.5 +/- 0.8 nmol/min/mg protein with glucose as substrate and 10.7 +/- 1.9 nmol/min/mg protein with lactate plus pyruvate (10:1) as substrate. Reintroduction of oxygen initiates complete (ouabain-sensitive) reuptake of K+ at initial rates of 35.4 +/- 3.2 nmol/min/mg protein and 18 +/- 1.7 nmol K+/min/mg protein, respectively. The rates of K+ leakage and reuptake fall when the pH is lowered from 7.4 to 6.0 but recover fully if the pH is raised to the original value. The rates of K+ release and uptake decrease when the Na+ concentration in the medium is decreased and increase when the Ca2+ concentration is decreased. The intrasynaptosomal [K+] under aerobic conditions was 77.3 +/- 3 mM and the calculated K+ diffusion potential was -72 mV. Anaerobic incubation of the synaptosomes from up to 20 min and at pH values from 7.4 to 6.0 did not produce irreversible impairment of any of the measured variables. These results suggest that permanent loss of brain function following prolonged hypoxia and ischemia is not due to irreversible damage to the synapses with respect to these parameters but rather to impairment of some other neuronal functions.
在等渗的菲可密度梯度上分离得到的突触体是研究神经元功能某些方面的有效模型。它们维持的代谢能量水平（[ATP]/[ADP][Pi]）和跨质膜电势与完整大脑中的神经元非常相似。在突触体悬浮液中同时监测外部介质中的K⁺浓度（K⁺敏感电极）、O₂摄取和细胞色素c还原（550nm减去540nm）。氧化代谢是突触体内ATP的主要来源，在pH 7.4时，以葡萄糖为底物进行无氧培养会导致K⁺以4.5±0.8 nmol/分钟/毫克蛋白质的速率泄漏，以乳酸加丙酮酸（10:1）为底物时则为10.7±1.9 nmol/分钟/毫克蛋白质。重新引入氧气后，K⁺开始以初始速率分别为35.4±3.2 nmol/分钟/毫克蛋白质和18±1.7 nmol K⁺/分钟/毫克蛋白质的速度进行完全（哇巴因敏感）再摄取。当pH从7.4降至6.0时，K⁺泄漏和再摄取的速率下降，但如果pH升高到原始值则会完全恢复。当培养基中的Na⁺浓度降低时，K⁺释放和摄取的速率降低，而当Ca²⁺浓度降低时则升高。有氧条件下突触体内的[K⁺]为77.3±3 mM，计算得出的K⁺扩散电位为-72 mV。将突触体在pH值为7.4至6.0的条件下进行长达20分钟的无氧孵育，并未对任何测量变量造成不可逆损伤。这些结果表明，长时间缺氧和缺血后大脑功能的永久性丧失并非由于突触在这些参数方面受到不可逆损伤，而是由于其他一些神经元功能受损。
