Ravindra R, Grosvenor C E
Department of Anatomy, Medical College of Georgia, Augusta 30912.
Endocrinology. 1988 Jan;122(1):114-9. doi: 10.1210/endo-122-1-114.
A [3H]colchicine-binding assay was employed for estimating the relative amounts of soluble and polymerized tubulin present in an individual anterior pituitary lobe. Colchicine binding to these two tubulin pools was time dependent and dose responsive. Scatchard analysis of the binding revealed that [3H]colchicine bound to both fractions with similar affinity. After establishing the optimal conditions for the binding assay, the effect of suckling on the relative levels of the two tubulin pools was studied. Groups of primiparous rats on days 12-14 postpartum were isolated from their pups for 4-5 h, then suckled for 30, 60, and 90 min, and killed, and the anterior pituitary lobes were dissected out. Each pituitary lobe was processed to obtain the two tubulin pools, viz. soluble and polymerized tubulin fractions. Suckling for 30 min resulted in an increase in soluble tubulin levels and a concomitant decrease in the polymerized pools. At 60 and 90 min, the soluble tubulin levels gradually decreased to presuckled levels, whereas the polymerized pools increased from the 30-min levels to those observed at 0 min. In another experiment, suckling for 10 min resulted in a decrease in the soluble tubulin levels and a corresponding increase in the polymerized tubulin pool. Treatment of nonsuckled rats with domperidone for 10 min also resulted in a shift of the equilibrium between the two tubulin pools similar to that observed at 10 min of suckling. Administration of bromocriptine 30 min beforehand to nonsuckled rats and then suckling them for 10 min blocked the suckling-induced rise in the polymerized tubulin levels. These results suggest a regulatory role for dopamine in the suckling-induced shift in the equilibrium between the soluble and polymerized tubulin pools in the anterior pituitary lobe.
采用[3H]秋水仙碱结合试验来估计单个垂体前叶中可溶性微管蛋白和聚合微管蛋白的相对含量。秋水仙碱与这两个微管蛋白库的结合具有时间依赖性和剂量反应性。对结合进行Scatchard分析表明，[3H]秋水仙碱以相似的亲和力与两个组分结合。在确定结合试验的最佳条件后，研究了哺乳对两个微管蛋白库相对水平的影响。将产后12 - 14天的初产大鼠组与幼崽隔离4 - 5小时，然后哺乳30、60和90分钟，随后处死，取出垂体前叶。对每个垂体前叶进行处理以获得两个微管蛋白库，即可溶性微管蛋白组分和聚合微管蛋白组分。哺乳30分钟导致可溶性微管蛋白水平升高，同时聚合微管蛋白库减少。在60和90分钟时，可溶性微管蛋白水平逐渐降至哺乳前水平，而聚合微管蛋白库则从30分钟时的水平增加到0分钟时观察到的水平。在另一项实验中，哺乳10分钟导致可溶性微管蛋白水平下降，聚合微管蛋白库相应增加。用多潘立酮处理未哺乳大鼠10分钟也导致两个微管蛋白库之间的平衡发生类似哺乳10分钟时观察到的变化。在未哺乳大鼠中预先30分钟给予溴隐亭，然后哺乳10分钟，可阻断哺乳诱导的聚合微管蛋白水平升高。这些结果表明多巴胺在哺乳诱导的垂体前叶可溶性微管蛋白和聚合微管蛋白库平衡变化中起调节作用。
