Patel T B, Sambasivarao D, Rashed H M
Department of Pharmacology, University of Tennessee, Memphis.
Arch Biochem Biophys. 1988 Aug 1;264(2):368-75. doi: 10.1016/0003-9861(88)90301-3.
The effect of veratridine-mediated depolarization on rat brain synaptosomal respiration in the presence and absence of calcium was investigated. Studies on respiration were performed employing three different pretreatments of the synaptosomes which attempted to deplete endogenous substrates. First, synaptosomes were preincubated for 10 min in the absence of any substrates in medium either containing or devoid of calcium. Second, synaptosomes were preincubated for either 15 or 60-min periods in the presence and absence of calcium, and the incubation medium was changed by centrifugation and resuspension of synaptosomes in their respective media. Irrespective of the prior treatment, maximal stimulation of respiration (400-600%) during veratridine (100 microM) elicited depolarization was observed only when calcium was present in the incubation media. In incubations performed in the absence of calcium, veratridine addition either modestly stimulated (10- and 15-min preincubated synaptosomes) or did not affect (60-min preincubated synaptosomes) the rate of respiration. However, when calcium was added back to these incubations the rate of respiration in the presence of veratridine was stimulated by five- to six-fold. Similarly, the rates of 14CO2 production from [1-14C]- and [2-14C]pyruvate were increased by veratridine only when synaptosomes were incubated in calcium-replete medium. These data indicate that calcium plays an obligatory role in depolarization-elicited stimulation of synaptosomal oxidative processes.
研究了藜芦碱介导的去极化在有钙和无钙情况下对大鼠脑突触体呼吸的影响。采用三种不同的突触体预处理方法进行呼吸研究，这些方法试图耗尽内源性底物。首先，将突触体在含或不含钙的培养基中无任何底物的情况下预孵育10分钟。其次，将突触体在有钙和无钙的情况下分别预孵育15或60分钟，通过离心和将突触体重悬于各自的培养基中来更换孵育培养基。无论先前的处理如何，仅当孵育培养基中存在钙时，在藜芦碱（100 microM）引起去极化期间才观察到呼吸的最大刺激（400 - 600%）。在无钙的孵育中，添加藜芦碱要么适度刺激呼吸速率（预孵育10分钟和15分钟的突触体），要么不影响呼吸速率（预孵育60分钟的突触体）。然而，当向这些孵育中重新添加钙时，在藜芦碱存在下的呼吸速率被刺激了五到六倍。同样，仅当突触体在富含钙的培养基中孵育时，藜芦碱才会增加[1 - 14C] - 和[2 - 14C] - 丙酮酸产生14CO2的速率。这些数据表明，钙在去极化引发的突触体氧化过程刺激中起关键作用。
