Huber C T, Solomon S S, Duckworth W C
J Clin Invest. 1980 Feb;65(2):461-8. doi: 10.1172/JCI109689.
Isolated fat cells from rat epididymal adipose tissue were preincubated with 50 microU/ml (0.33 nM) 125I-insulin at 23 degrees C to enhance binding while retarding degradation. The fat cells were then perifused at that temperature to remove unbound 125I-insulin, and fractions of perifusate were collected each minute. The temperature of the cells in the perifusion chamber was then rapidly increased to 37 degrees C, and perifusion was continued. The fat cells degraded a portion of the bound 125I-insulin measured by loss of immunoprecipitability with excess antisera to insulin. The percentage of degraded 125I-insulin dissociating from the fat cells increased progressively with time at 37 degrees C, and the rateof dissociation of 125I-insulin degradation products showed a first-order dependence on the amount of degraded 125I-insulin bound to the cells. To explain this first-order dependence it is necessary to postulate a "processing" step after binding and before degradation. The first-order rate constant at 37 degrees C is 0.023 +/- 0.004 min-1. Fast and slow dissociating components can be resolved from kinetic plots of the dissociation of undegraded 125I-insulin (immunoprecipitable) from the isolated fat cells. The antilipolytic activity of the 125I-insulin on epinephrine-stimulated lipolysis is evident over much of the time-course of dissociation. A model for the degradation of insulin bound to isolated fat cells is discussed.
从大鼠附睾脂肪组织分离出的脂肪细胞，在23℃下用50微单位/毫升（0.33纳摩尔）的125I胰岛素进行预孵育，以增强结合并减缓降解。然后在该温度下对脂肪细胞进行灌流，以去除未结合的125I胰岛素，每分钟收集灌流液的部分。接着将灌流室中细胞的温度迅速升至37℃，并继续灌流。脂肪细胞降解了一部分结合的125I胰岛素，这通过用过量抗胰岛素抗血清检测免疫沉淀性的丧失来测定。在37℃下，从脂肪细胞中解离的降解125I胰岛素的百分比随时间逐渐增加，并且125I胰岛素降解产物的解离速率对与细胞结合的降解125I胰岛素的量呈一级依赖性。为了解释这种一级依赖性，有必要假定在结合后和降解前存在一个“加工”步骤。37℃下的一级速率常数为0.023±0.004分钟-1。从未降解的125I胰岛素（可免疫沉淀）从分离的脂肪细胞解离的动力学图中可以分辨出快速和缓慢解离成分。在解离的大部分时间过程中，125I胰岛素对肾上腺素刺激的脂肪分解的抗脂解活性是明显的。本文讨论了结合在分离脂肪细胞上的胰岛素的降解模型。
