Donkin S S, Armentano L E
Department of Dairy Science, University of Wisconsin, Madison 53706, USA.
J Anim Sci. 1995 Feb;73(2):546-51. doi: 10.2527/1995.732546x.
Hepatocyte monolayers were established from young preruminating (7 to 14 d of age) or older ruminating (11 to 12 wk of age) calves and used to evaluate the effects of insulin and glucagon on incorporation of carbon from 2.5 mM [2-14C]propionate and 2.0 mM [U-14C]lactate into glucose and glycogen. Developmental state (young preruminating vs older ruminating) of the donor calf did not affect the rate of gluconeogenesis from propionate in the absence of hormones. Insulin decreased (P < .05) gluconeogenesis and increased (P < .05) glycogenesis from propionate and lactate in hepatocytes from preruminating calves but had no effect on hepatocytes from ruminating calves. Lactate was poorly metabolized to glucose and was not responsive to glucagon in hepatocytes from ruminating calves compared with hepatocytes from preruminating calves. Hepatocytes responded to glucagon by increasing (P < .05) gluconeogenesis from propionate. Maximal responsiveness to glucagon did not differ between ruminating and preruminating calves, but hepatocytes from preruminating calves responded at lower glucagon concentrations (P < .05). These data demonstrate a similar capacity of hepatocytes from preruminating and ruminating calves to metabolize propionate to glucose, but there was a seven- to eightfold decrease in gluconeogenesis from lactate in ruminating calves that was accompanied by a decreased response to acute changes in insulin and glucagon.
从幼龄反刍前（7至14日龄）或老龄反刍期（11至12周龄）犊牛建立肝细胞单层培养物，并用于评估胰岛素和胰高血糖素对2.5 mM [2-¹⁴C]丙酸盐和2.0 mM [U-¹⁴C]乳酸盐中的碳掺入葡萄糖和糖原的影响。供体犊牛的发育状态（幼龄反刍前与老龄反刍期）在无激素情况下不影响丙酸盐的糖异生速率。胰岛素降低了（P < 0.05）反刍前犊牛肝细胞中丙酸盐的糖异生，并增加了（P < 0.05）丙酸盐和乳酸盐的糖原生成，但对反刍期犊牛的肝细胞没有影响。与反刍前犊牛的肝细胞相比，反刍期犊牛的肝细胞中乳酸转化为葡萄糖的代谢较差，且对胰高血糖素无反应。肝细胞通过增加（P < 0.05）丙酸盐的糖异生来响应胰高血糖素。反刍期和反刍前犊牛对胰高血糖素的最大反应性没有差异，但反刍前犊牛的肝细胞在较低的胰高血糖素浓度下就有反应（P < 0.05）。这些数据表明，反刍前和反刍期犊牛的肝细胞将丙酸盐代谢为葡萄糖的能力相似，但反刍期犊牛乳酸糖异生减少了7至8倍，同时对胰岛素和胰高血糖素急性变化的反应也降低。
