Carvounis C P, Franki N, Levine S D, Hays R M
J Membr Biol. 1979 Sep;49(3):253-68. doi: 10.1007/BF01871121.
Vsopressin activates a number of transport systems in the toad bladder, including the systems for water, urea, sodium, and other small solutes. Evidence from experiments with selective inhibitors indicates that these transport systems are to a large extent functionally independent. In the present study, we show that the transport systems can be separately activated. Low concentrations of vasopressin (1 mU/ml) activate urea transport with virtually no effect on water transport. This selective effect is due in part to the relatively greater inhibitor action of endogenous prostaglandins on water transport. Low concentrations of 8-bromoadenosine cyclic AMP, on the other hand, activate water, but not urea transport. In additional experiments, we found that varying the ratio of exogenous cyclic AMP to theophylline activated water or urea transport selectively. These studies support the concept of independently controlled systems for water and solute transport, and provide a basis for the study of individual luminal membrane pathways for water and solutes in the accompanying paper.
加压素激活蟾蜍膀胱中的多种转运系统，包括水、尿素、钠和其他小分子溶质的转运系统。选择性抑制剂实验的证据表明，这些转运系统在很大程度上功能独立。在本研究中，我们表明这些转运系统可以被分别激活。低浓度的加压素（1 mU/ml）激活尿素转运，而对水转运几乎没有影响。这种选择性作用部分归因于内源性前列腺素对水转运相对更强的抑制作用。另一方面，低浓度的8-溴腺苷环磷酸激活水转运，但不激活尿素转运。在另外的实验中，我们发现改变外源性环磷酸腺苷与茶碱的比例可选择性地激活水或尿素转运。这些研究支持水和溶质转运系统独立控制的概念，并为随附论文中研究水和溶质的单个管腔膜途径提供了基础。
