Dubé C, Vallières S, Ethier C, Benbrahim N, Tremblay C, Gascon-Barré M
André-Viallet Clinical Research Center, St. Luc Hospital, Montreal, Quebec, Canada.
Hepatology. 1991 Mar;13(3):489-99. doi: 10.1002/hep.1840130317.
To test further the competence of the cirrhotic liver to metabolize vitamin D3 at C-25, hepatocytes were isolated from controls and from CCl4-induced cirrhotic rat livers, as well as from partially hepatectomized rats. The transformation of D3 into 25-hydroxyvitamin D3 was studied in the presence of 10(7) hepatocytes at D3 concentrations of 20 nmol/L to 15.4 mumol/L. Histologically, micronodular cirrhosis was present in all CCl4-treated rats, whereas controls had normal livers; portal venous pressure (p less than 0.008) and intrahepatic collagen content (p less than 0.0001) were significantly increased in CCl4-treated rats, whereas no difference was found between the two groups in the total and ionized serum calcium, D3 metabolites, ALT, AST and alkaline phosphatase. Cytochrome P-450 was 0.27 +/- 0.02 and 0.25 +/- 0.02 nmol/10(6) hepatocytes in controls and cirrhotic rats (N.S.), and it significantly increased in both groups after phenobarbital or 3-methylcholanthrene administration (p less than 0.0001). 25-Hydroxyvitamin D3 formation was best described by power law equations and varied between 0.02 +/- 0.0004 and 29.57 +/- 2.8 in controls, and 0.024 +/- 0.0004 and 32.0 +/- 7.0 pmol.hr-1.10(6) hepatocytes-1 in cirrhotic rats. No statistically significant difference was found in the slopes of the 25-hydroxyvitamin D3 formation, but the y-axis intercept was found to be lower in cirrhotic rats under basal resting conditions (p less than 0.005). Inducers of the mixed function oxidases significantly increased 25-hydroxyvitamin D3 formation in controls as well as in cirrhotic rats (p less than 0.005). Moreover, both groups were found to respond similarly to the addition of modulators of the enzyme such as the calcium ionophore A23187 and parathyroid hormone. Partial hepatectomy was also without effect on the activation of D3. Furthermore, the cell sequestration of D3 was also found to be unperturbed in hepatocytes obtained from either cirrhotic or partially hepatectomized livers. The data indicate that in well-compensated micronodular cirrhosis, the C-25 hydroxylation of D3 is generally intrinsically normal at the cellular level and that it also remains fully responsive to in vivo and in vitro modulators of its activity.
为了进一步检测肝硬化肝脏在C-25位代谢维生素D3的能力，从对照组、四氯化碳诱导的肝硬化大鼠肝脏以及部分肝切除的大鼠中分离出肝细胞。在含有10⁷个肝细胞、维生素D3浓度为20 nmol/L至15.4 μmol/L的条件下，研究了D3向25-羟基维生素D3的转化。组织学检查显示，所有经四氯化碳处理的大鼠均存在小结节性肝硬化，而对照组肝脏正常；经四氯化碳处理的大鼠门静脉压力（p<0.008）和肝内胶原含量（p<0.0001）显著增加，而两组在总血清钙和离子化血清钙、D3代谢产物、谷丙转氨酶、谷草转氨酶和碱性磷酸酶方面未发现差异。对照组和肝硬化大鼠肝细胞中的细胞色素P-450分别为0.27±0.02和0.25±0.02 nmol/10⁶个肝细胞（无显著差异），给予苯巴比妥或3-甲基胆蒽后两组均显著增加（p<0.0001）。25-羟基维生素D3的形成可用幂律方程最好地描述，对照组中其值在0.02±0.0004至29.57±2.8之间，肝硬化大鼠中为0.024±0.0004至32.0±7.0 pmol·hr⁻¹·10⁶个肝细胞⁻¹。25-羟基维生素D3形成的斜率未发现统计学显著差异，但在基础静息条件下，肝硬化大鼠的y轴截距较低（p<0.005）。混合功能氧化酶诱导剂在对照组和肝硬化大鼠中均显著增加25-羟基维生素D3的形成（p<0.005）。此外，发现两组对添加酶调节剂如钙离子载体A23187和甲状旁腺激素的反应相似。部分肝切除对D3的激活也无影响。此外，在从肝硬化或部分肝切除的肝脏获得的肝细胞中，D3的细胞摄取也未受到干扰。数据表明，在代偿良好的小结节性肝硬化中，D3的C-25羟化在细胞水平上总体上本质上是正常的，并且对其活性的体内和体外调节剂仍保持完全反应性。
