Hong C D, Essig A
J Membr Biol. 1976 Aug 26;28(2-3):121-42. doi: 10.1007/BF01869693.
The effects of various agents on active sodium transport were studied in the toad bladder in terms of the equivalent circuit comprising an active conductance Ka, an electromotive force ENa, and a parallel passive conductance Kp. For agents which affect Ka, but not ENa or Kp, the inverse slope of the plot of total conductance K against short-circuit current IO evaluates ENa, and the intercept represents Kp. Studies employing 5 X 10(-7) M amiloride to depress Ka indicate a changing ENa, invalidating the use of the slope technique with this agent. An alternative suitable technique employs 10(-5) M amiloride, which reduces IO reversibly to near zero without effect on Kp. Despite curvilinearity of the K-IO plot under these conditions, Kp may therefore be estimated fairly precisely from the residual conductance. It then becomes possible to follow the dynamic behavior of Ka and ENa (in the absence of 10(-5) M amiloride) by frequent measurements of K and IO, utilizing the relationships Ka=K-Kp, and ENa=IO/(K-Kp). 2-deoxy-D-glucose (7.5 X 10(-3)M) depressed both Ka and ENa. All of the above effects were noted promptly; Kp was unaffected. The "electromotive force of Na transport" ENa appears not to be a pure energetic parameter, but to relfect kinetic factors as well, in accordance with thermodynamic considerations.
根据由主动电导Ka、电动势ENa和并联的被动电导Kp组成的等效电路，研究了各种药剂对蟾蜍膀胱主动钠转运的影响。对于影响Ka但不影响ENa或Kp的药剂，总电导K对短路电流IO作图的反斜率可用来评估ENa，而截距代表Kp。使用5×10⁻⁷M氨氯吡脒抑制Ka的研究表明ENa会发生变化，因此不能用该药剂的斜率技术。另一种合适的技术是使用10⁻⁵M氨氯吡脒，它可使IO可逆地降低至接近零而不影响Kp。尽管在这些条件下K-IO图呈曲线关系，但仍可根据残余电导相当精确地估算Kp。这样就有可能通过频繁测量K和IO来跟踪Ka和ENa的动态行为（在不存在10⁻⁵M氨氯吡脒的情况下），利用关系Ka = K - Kp和ENa = IO/(K - Kp)。2-脱氧-D-葡萄糖（7.5×10⁻³M）使Ka和ENa均降低。上述所有影响均迅速出现；Kp未受影响。“钠转运的电动势”ENa似乎不是一个纯粹的能量参数，而是根据热力学考虑也反映动力学因素。
