REGULATION OF SUGAR TRANSPORT IN MUSCLE

青蛙缝匠肌的蛋白质通过孵育肌肉来标记 [~3H]-苯丙氨酸或[14C]苯丙氨酸。一条主要的标记蛋白条带， 表观分子量约为96,000，可在 标记质膜的十二烷基硫酸钠-聚丙烯酰胺凝胶。这 肌浆网蛋白条带可被区分 和线粒体片段。短暂电刺激收缩 分离的，标记的肌肉导致明确的，选择性的丧失 所描述的质膜蛋白带区域的放射性 上面。我们建议更详细地研究这一新的观察结果。一个 我们将尝试分离和鉴定这种膜蛋白 会因收缩而改变。初步研究表明， 肌肉中钙离子的浓度会导致肌肉痉挛，还会导致 以类似的方式减少标记的质膜蛋白的量 对电刺激的影响。据推测，肌肉 收缩可能伴随着依赖于钙离子的蛋白酶的激活， 在中性pH时最活跃，已知存在于肌肉和 这种酶在生理条件下可能攻击特定的膜蛋白 条件。众所周知，体内运动和肌肉收缩 体外培养伴随着肌肉通透性的长期增加 从细胞到糖。将尝试查看是否存在 膜蛋白的变化与血管紧张素转换酶活性增加之间的相关性 渗透性。这些事件的时间进程及其影响 我们将研究蛋白质分解的抑制剂。渗透率的变化 糖对于适当的营养和营养至关重要 肌肉的功能。拟议的研究是一项长期研究的一部分 糖类运输调控方式的研究 骨骼肌细胞。

Proteins of frog sartorius muscles were labeled by incubating muscles with either [3H]- or [14C]phenylalanine. A major, labeled protein band, apparent molecular weight approximately 96,000, was distinguishable in SDS-polyacrylamide electrophoretic gels of labeled plasma membranes. This band could be differentiated from protein bands of sarcoplasmic reticulum and mitochondrial fractions. Brief electrical stimulation of contraction of isolated, labeled muscles caused a definite, selective loss of radioactivity in the region of the plasma membrane protein band described above. We propose to study this new observation in greater detail. An attempt will be made to isolate and characterize the membrane protein that is altered by contraction. Preliminary studies have shown that an increase in concentration of Ca++ in muscles causes contracture and also leads to a diminution in amount of labeled plasma membrane protein in a manner similar to the effect of electrical stimulation. It is postulated that muscle contraction may be accompanied by activation of a Ca++ dependent protease, optimally active at neutral pH, that is known to be present in muscle and that this enzyme may attack specific membrane proteins under physiological conditions. It is known that exercise in vivo and muscle contraction in vitro are accompanied by a prolonged increase in permeability of muscle cells to sugar. An attempt will be made to see whether or not there is a correlation between changes in membrane proteins and an increase in permeability. The time course of these events and the effects of inhibitors of proteolysis will be examined. Changes in permeability to sugar are of fundamental importance for the proper nutrition and functioning of muscle. The proposed studies are part of a long-term investigation of the manner in which sugar transport is regulated in skeletal muscle cells.