Kitasato H, Sato S, Murayama K, Nishio K
Jpn J Physiol. 1980;30(1):115-30. doi: 10.2170/jjphysiol.30.115.
The effects of insulin and ouabain on 22Na efflux and net Na loss were examined in frog sartorius muscles. After removal of ouabain, 22Na efflux which had been inhibited by ouabain remained at the inhibited level for more than 2 hr. In ouabain-free solution, insulin stimulated the Na efflux from ouabain-preincubated muscles. The stimulating effect of insulin on 22Na efflux was completely blocked by the presence of ouabain. Insulin shifted the Na efflux vs. intracellular Na concentration relationship toward the region of lower Na concentrations, and made the slope of log (Na efflux) vs. log [Na]1 relationship less step. On the other hand, ouabain shifted the Na efflux vs. intracellular Na concentration relationship toward the region of higher Na concentration, and made the slope of the log (Na efflux) vs. log [Na]1 relationship steeper. The relationship between insulin-stimulated Na efflux and intracellular Na concentration obtained from ouabain-preincubated muscle was located in the region of higher Na concentrations than that obtained from control muscle. These findings suggest that insulin increases an apparent affinity of binding sites for Na ions, and the possibility that insulin increases the Vmax of Na transport system may be excluded. In contrast with the effect of insulin, ouabain may be considered to decrease the apparent affinity of binding site for Na ions.
研究了胰岛素和哇巴因对蛙缝匠肌22Na外流和净钠丢失的影响。去除哇巴因后，先前被哇巴因抑制的22Na外流在抑制水平持续超过2小时。在无哇巴因溶液中，胰岛素刺激了经哇巴因预孵育肌肉的钠外流。胰岛素对22Na外流的刺激作用被哇巴因完全阻断。胰岛素使钠外流与细胞内钠浓度的关系向较低钠浓度区域移动，并使log(钠外流)与log[Na]1关系的斜率变小。另一方面，哇巴因使钠外流与细胞内钠浓度的关系向较高钠浓度区域移动，并使log(钠外流)与log[Na]1关系的斜率变陡。从经哇巴因预孵育肌肉获得的胰岛素刺激的钠外流与细胞内钠浓度之间的关系位于比从对照肌肉获得的关系更高的钠浓度区域。这些发现表明，胰岛素增加了钠离子结合位点的表观亲和力，并且可以排除胰岛素增加钠转运系统Vmax的可能性。与胰岛素的作用相反，哇巴因可能被认为降低了钠离子结合位点的表观亲和力。
