首页>
外文期刊>The biochemical journal
>Respiration-dependent calcium ion uptake by two preparations of cardiac mitochondria. Effects of palmitoyl-coenzyme A and palmitoylcarnitine on calcium ion cycling and nicotinamide nucleotide reduction state
【24h】
Respiration-dependent calcium ion uptake by two preparations of cardiac mitochondria. Effects of palmitoyl-coenzyme A and palmitoylcarnitine on calcium ion cycling and nicotinamide nucleotide reduction state
pCasup2+/sup uptake and the effect of the uptake inhibitors palmitoyl-CoA and palmitoylcarnitine were examined in two preparations of dog cardiac mitochondria. Mitochondria prepared by using the Nagarse technique was 2.5-fold more active in respiration-dependent Casup2+/sup uptake than were mitochondria isolated by using the Polytron procedure. Palmitoyl-CoA and palmitoylcarnitine inhibited Casup2+/sup uptake in both preparations uncompetitively, with iK/isubi,app/sub 0.4 and 20μm. Casup2+/sup-uptake rates were related to, or influenced by, the concentration of mitochondrial reduced nicotinamide nucleotides, with uptake slowing as this concentration decreased. When most of the nicotinamide nucleotides was oxidized, Casup2+/sup release and respiratory stimulation were observed. In the presence of Ruthenium Red and palmitoyl-CoA, oxidation of nicotinamide nucleotides was abolished and the time to Casup2+/sup release was shortened corresponding to the time of onset of nicotinamide nucleotide oxidation in the absence of Ruthenium Red. The results suggest that NAD(P)H oxidation in the presence of rotenone was a consequence of Casup2+/sup re-uptake and that net Casup2+/sup release could be observed as reduced nicotinamide nucleotide concentrations declined. Although nicotinamide nucleotide oxidation occurred in the presence of rotenone, it was not linked in an apparent manner to acyl-group metabolism (palmitoylcarnitine was less effective than palmitoyl-CoA). Therefore either a by-pass of the rotenone block or a direct interaction of NAD(P)H with the Casup2+/sup-uptake process was possible. Loss of NADH occurred before respiratory stimulation, and this loss may relate to decreased coupling efficiency at sites 2 and 3 of the respiratory chain, as suggested by others [Bhuvaneswaran & Wadkins (1978) iBiochem. Biophys. Res. Commun./ib82/b, 648–654]./p
展开▼
机译：在两种犬心脏线粒体制剂中研究了> Ca 2 + 的摄取以及摄取抑制剂palmitoyl-CoA和palmittoylcarnitine的作用。使用Nagarse技术制备的线粒体在呼吸依赖性Ca 2 + 吸收中的活性是通过Polytron程序分离的线粒体的2.5倍。棕榈酰辅酶A和棕榈酰肉碱在两种制剂中均无竞争性地抑制Ca 2 + 的吸收， K i，app 为0.4和20μm。 Ca 2 + 的吸收速率与线粒体还原烟酰胺核苷酸的浓度有关，或受其影响，随着该浓度的降低，其吸收速度减慢。当大多数烟酰胺核苷酸被氧化时，观察到Ca 2 + 的释放和呼吸刺激。在存在钌红和棕榈酰-CoA的情况下，烟酰胺核苷酸的氧化被消除，并且与在不存在钌红的情况下烟酰胺核苷酸氧化开始的时间相对应，Ca 2 + 释放的时间缩短了。结果表明，鱼藤酮存在下NAD（P）H的氧化是Ca 2 + 再摄取的结果，并且可以观察到Ca 2 + 的净释放为降低烟酰胺核苷酸浓度下降。尽管在鱼藤酮的存在下会发生烟酰胺核苷酸氧化，但烟酸未以明显的方式与酰基基团代谢联系在一起（棕榈酰肉碱的效力不如棕榈酰辅酶A）。因此，鱼藤酮嵌段的旁路或NAD（P）H与Ca 2 + 吸收过程的直接相互作用都是可能的。 NADH的损失发生在呼吸刺激之前，这种损失可能与呼吸链第2位和第3位的偶联效率降低有关，正如其他人所建议的那样[Bhuvaneswaran＆amp; A. Wadkins（1978），生物化学。生物物理学。 Res。 82 ，648–654]。
展开▼
