Iwazumi T, Pollack G H
J Cell Physiol. 1981 Mar;106(3):321-37. doi: 10.1002/jcp.1041060302.
It has proved difficult to activate skinned muscle fibers to produce high tension (3 kg/cm2 level) without loss of clear striations. A new method was developed which permits high tension production in skinned muscle fibers while retaining clear striations. Clear striations allow reliable measurement of the sarcomere lengths during contraction by microscopy and diffractometry. The method is to increase the Ca++ concentration of the bathing solution very gradually over a time period of 5 to 10 minutes. Once the skinned fiber is conditioned by this slow activation, subsequent contractions can be elicited by ordinary quick activations without loss of striations. When the experiments are carried out with careful controls for the uniformity of the sarcomere length distribution along the entire length of the fiber, contractions are highly repeatable. Using the new method and stringent quality control of fibers, the sarcomere length-isometric tension relationship of skinned rabbit soleus fibers was obtained. The results differ from those previously obtained by conventional activation methods in that tension increases with sarcomere length not only at low (pCa = 5.8), but also at high (pCa = 5.2), calcium concentration.
事实证明，要激活去表皮肌纤维以产生高张力（3千克/平方厘米水平）而又不丧失清晰的条纹是很困难的。人们开发了一种新方法，该方法能够在去表皮肌纤维中产生高张力，同时保留清晰的条纹。清晰的条纹使得通过显微镜和衍射测量法在收缩过程中可靠地测量肌节长度成为可能。该方法是在5到10分钟的时间段内非常缓慢地增加浴液中的钙离子浓度。一旦通过这种缓慢激活使去表皮纤维适应，随后的收缩就可以通过普通的快速激活引发，而不会丧失条纹。当沿着纤维的整个长度对肌节长度分布的均匀性进行仔细控制来进行实验时，收缩具有高度的可重复性。使用这种新方法并对纤维进行严格的质量控制，得到了去表皮兔比目鱼肌纤维的肌节长度-等长张力关系。结果与先前通过传统激活方法获得的结果不同，即不仅在低钙浓度（pCa = 5.8）下，而且在高钙浓度（pCa = 5.2）下，张力都随肌节长度增加。
