Lapointe D S, Hanahan D J, Olson M S
Biochemistry. 1987 Mar 24;26(6):1568-74. doi: 10.1021/bi00380a012.
In the perfused rat liver, platelet activating factor, 1-O-hexadecyl-2-acetyl-sn-glycero-3-phosphocholine (AGEPC), infusion produces an extensive but transient glycogenolytic response which at low AGEPC concentrations (i.e., 10(-11) M) is markedly dependent upon the perfusate calcium levels. The role of calcium in the glycogenolytic response of the liver to AGEPC was investigated by assessing the effect of AGEPC on various calcium pools in the intact liver. Livers from fed rats were equilibrated with 45Ca2+, and the kinetics of 45Ca2+ efflux were determined in control, AGEPC-stimulated, and phenylephrine-stimulated livers during steady-state washout of 45Ca2+. AGEPC treatment had only a slight if any effect on the pattern of steady-state calcium efflux from the liver, as opposed to major perturbations in the pattern of calcium efflux effected by the alpha-adrenergic agonist phenylephrine. Infusion of short pulses of AGEPC during the washout of 45Ca2+ from labeled livers caused a transient release of 45Ca2+ which was not abolished at low calcium concentrations in the perfusate. Moreover, there occurred no appreciable increase in the total calcium content in the liver perfusate at either high or low concentrations of calcium in the perfusion fluid. Infusion of latex beads, which are removed by the reticuloendothelial cells, caused the release of hepatic 45Ca2+ in a fashion similar to the case with AGEPC. Our findings indicate that AGEPC does not perturb a major pool of calcium within the liver as occurs upon alpha-adrenergic stimulation; it is likely that AGEPC mobilizes calcium from a smaller yet very important pool, very possibly from nonparenchymal cells in the liver.
在灌注大鼠肝脏中，输注血小板活化因子1-O-十六烷基-2-乙酰基-sn-甘油-3-磷酸胆碱（AGEPC）会产生广泛但短暂的糖原分解反应，在低AGEPC浓度（即10⁻¹¹ M）时，该反应明显依赖于灌注液中的钙水平。通过评估AGEPC对完整肝脏中各种钙库的影响，研究了钙在肝脏对AGEPC糖原分解反应中的作用。给喂食大鼠的肝脏用⁴⁵Ca²⁺平衡，在⁴⁵Ca²⁺的稳态洗脱过程中，测定对照、AGEPC刺激和去氧肾上腺素刺激的肝脏中⁴⁵Ca²⁺流出的动力学。与α-肾上腺素能激动剂去氧肾上腺素对钙流出模式的主要扰动相反，AGEPC处理对肝脏稳态钙流出模式的影响即使有也很轻微。在从标记肝脏洗脱⁴⁵Ca²⁺期间输注短脉冲的AGEPC会导致⁴⁵Ca²⁺的短暂释放，在灌注液低钙浓度时这种释放不会被消除。此外，无论灌注液中钙浓度高或低，肝脏灌注液中的总钙含量均未出现明显增加。输注被网状内皮细胞清除的乳胶珠，会以与AGEPC类似的方式导致肝脏⁴⁵Ca²⁺的释放。我们的研究结果表明，AGEPC不会像α-肾上腺素能刺激那样扰乱肝脏内的主要钙库；AGEPC很可能从一个较小但非常重要的钙库中动员钙，很可能是从肝脏中的非实质细胞中动员钙。
