Bentley P J
J Endocrinol. 1975 Oct;67(1):119-25. doi: 10.1677/joe.0.0670119.
The electrical potential difference and short-circuit current (scc, reflecting active transmural sodium transport) across the toad urinary bladder in vitro was unaffected by the presence of hypo-osmotic solutions bathing the mucosal (urinary) surface, providing that the transmural flow of water was small. Vasopressin increased the scc across the toad bladder (the natriferic response), but this stimulation was considerably reduced in the presence of a hypo-osmotic solution on the mucosal side, conditions under which water transfer across the membrane was also increased. This inhibition of the natriferic response did not depend on the direction of the water movement, for if the osmotic gradient was the opposite way to that which normally occurs, the response to vasopressin was still reduced. The natriferic response to cyclic AMP was also inhibited in the presence of an osmotic gradient. Aldosterone increased the scc and Na+ transport across the toad bladder but this response was not changed when an osmotic gradient was present. The physiological implications of these observations and the possible mechanisms involved are discussed.
体外蟾蜍膀胱的跨膜电位差和短路电流（scc，反映钠的主动跨壁转运）不受低渗溶液浴于黏膜（尿液）表面的影响，前提是跨壁水流较小。血管升压素增加蟾蜍膀胱的短路电流（排钠反应），但在黏膜侧存在低渗溶液时，这种刺激会显著减弱，此时跨膜水转运也会增加。这种对排钠反应的抑制并不取决于水的移动方向，因为如果渗透梯度与正常情况相反，对血管升压素的反应仍然会降低。在存在渗透梯度时，对环磷酸腺苷的排钠反应也会受到抑制。醛固酮增加蟾蜍膀胱的短路电流和钠转运，但当存在渗透梯度时，这种反应没有变化。讨论了这些观察结果的生理学意义及可能涉及的机制。
