Quinlan P T, Halestrap A P
Biochem J. 1986 Jun 15;236(3):789-800. doi: 10.1042/bj2360789.
The effects of hormones on the cytochrome spectra of isolated hepatocytes were recorded under conditions of active gluconeogenesis from L-lactate. Glucagon, phenylephrine, vasopressin and valinomycin, at concentrations that caused stimulation of gluconeogenesis, increased the reduction of the components of the cytochrome bc1 complex, just as has been observed in liver mitochondria isolated from glucagon-treated rats [Halestrap (1982) Biochem. J. 204, 37-47]. The effects of glucagon and phenylephrine were additive. The time courses of the increased reduction of cytochrome c/c1 and NAD(P)H/NAD(P)+ caused by hormones, valinomycin, A23187 and ethanol were measured by dual-beam spectrophotometry and fluorescence respectively. Ethanol (14 mM) produced a substantial rise in NAD(P)H fluorescence, beta-hydroxybutyrate/acetoacetate and lactate/pyruvate ratios, no change in cytochrome c/c1 reduction, a 10% decrease in O2 consumption and a 60% decrease in gluconeogenesis. Glucagon, phenylephrine and vasopressin caused a substantial and transient rise in NAD(P)H fluorescence, but a sustained increase in cytochrome c/c1 reduction and the rates of O2 consumption and gluconeogenesis. The transience of the fluorescence response was greater in the absence of Ca2+, when the cytochrome c/c1 response also became transient. The fluorescence response was smaller and less transient, but the cytochrome c/c1 response was greater, in the presence of fatty acids. Both responses were greatly decreased by the presence of 1 mM-pent-4-enoate. Valinomycin (2.5 nM) caused a decrease in NAD(P)H fluorescence coincident with an increase in cytochrome c/c1 reduction and the rate of gluconeogenesis and O2 consumption. A23187 (7.5 mM) caused increases in both NAD(P)H fluorescence and cytochrome c/c1 reduction. The effects of hormones and valinomycin on the time courses of NAD(P)H fluorescence, cytochrome c/c1 reduction and light-scattering by hepatocytes were compared with those of 0.5 microM-Ca2+ or 1 nM-valinomycin on the same parameters of isolated liver mitochondria. It is concluded that hormones increase respiration by hepatocytes in a biphasic manner. An initial Ca2+-dependent activation of mitochondrial dehydrogenases rapidly increases the mitochondrial [NADH], which is followed by a volume-mediated stimulation of fatty acid oxidation and electron flow between NADH and cytochrome c. 10. Amytal (0.5 mM) was able to reverse the effects of hormones on the reduction of cytochromes c/c1 and the rates of gluconeogenesis and O2 consumption without significantly lowering tissue [ATP].(ABSTRACT TRUNCATED AT 400 WORDS)
在以L-乳酸进行活跃糖异生的条件下，记录了激素对分离的肝细胞细胞色素光谱的影响。胰高血糖素、去氧肾上腺素、血管加压素和缬氨霉素在能刺激糖异生的浓度下，增加了细胞色素bc1复合物各组分的还原程度，这与从经胰高血糖素处理的大鼠分离出的肝线粒体中观察到的情况相同[哈勒斯屈普（1982年）《生物化学杂志》204卷，37 - 47页]。胰高血糖素和去氧肾上腺素的作用是相加的。通过双光束分光光度法和荧光法分别测量了激素、缬氨霉素、A23187和乙醇引起的细胞色素c/c1及NAD(P)H/NAD(P)+还原增加的时间进程。乙醇（14 mM）使NAD(P)H荧光、β-羟丁酸/乙酰乙酸和乳酸/丙酮酸比值大幅升高，细胞色素c/c1还原无变化，氧气消耗减少10%，糖异生减少60%。胰高血糖素、去氧肾上腺素和血管加压素使NAD(P)H荧光大幅且短暂升高，但细胞色素c/c1还原、氧气消耗率和糖异生率持续增加。在无Ca2+时荧光反应的短暂性更强，此时细胞色素c/c1反应也变得短暂。在有脂肪酸存在时，荧光反应较小且不太短暂，但细胞色素c/c1反应更大。1 mM - 4 - 戊烯酸的存在使两种反应都大幅降低。缬氨霉素（2.5 nM）使NAD(P)H荧光降低，同时细胞色素c/c1还原增加以及糖异生率和氧气消耗率增加。A23187（7.5 mM）使NAD(P)H荧光和细胞色素c/c1还原都增加。将激素和缬氨霉素对肝细胞NAD(P)H荧光、细胞色素c/c1还原和光散射时间进程的影响，与0.5 microM - Ca2+或1 nM - 缬氨霉素对分离肝线粒体相同参数的影响进行了比较。得出的结论是，激素以双相方式增加肝细胞的呼吸作用。线粒体脱氢酶最初的Ca2+依赖性激活迅速增加线粒体[NADH]，随后是体积介导的脂肪酸氧化刺激以及NADH与细胞色素c之间的电子流。10. 阿米妥（0.5 mM）能够逆转激素对细胞色素c/c1还原、糖异生率和氧气消耗率的影响，而不会显著降低组织[ATP]。（摘要截取自400字）
