Greenwell J R, Low H S
J Membr Biol. 1981;61(2):91-6. doi: 10.1007/BF02007635.
Frog skin was mounted in an Ussing chamber and the actions of caerulein, gastrin, pentagastrin, and secretin on the active transport of sodium were studied using the short-circuit current method. All polypeptides exerted their effect when placed in the solution bathing the outside surface of the skin. The response was a transient dose-related increase in the transepithelial electrical potential difference and in the short-circuit current. Analysis of the response indicated that at submaximal doses the effect was due to an increase in the rate of entry of sodium through the outer barrier to active sodium transport. At supramaximal doses the passive permeability of the skin was also increased. Th ED50 concentrations of the hormones were: caerulein, 50 pM; gastrin, 53 pM; pentagastrin, 440 pM; and secretin, 30 pM. It is argued that the large quantity of caerulein or caerulein-like peptides stored in the skin may be required either to control the entry of sodium when the amphibian is undergoing maximum stress in a freshwater environment, or that it may have a protective function for the amphibian as it could elicit a noxious hypersecretion in the gastrointestinal tract of the predator together with a marked hypotension.
将蛙皮置于尤斯灌流小室中，采用短路电流法研究了蛙皮素、胃泌素、五肽胃泌素和促胰液素对钠主动转运的作用。所有多肽置于浸泡皮肤外表面的溶液中时均发挥作用。反应是跨上皮电势差和短路电流出现与剂量相关的短暂增加。对反应的分析表明，在亚最大剂量时，作用是由于钠通过主动钠转运的外部屏障进入的速率增加。在超最大剂量时，皮肤的被动通透性也增加。这些激素的半数有效浓度（ED50）分别为：蛙皮素50皮摩尔；胃泌素53皮摩尔；五肽胃泌素440皮摩尔；促胰液素30皮摩尔。有人认为，皮肤中储存的大量蛙皮素或类蛙皮素肽可能是在两栖动物处于淡水环境中承受最大压力时用于控制钠的进入，或者它可能对两栖动物具有保护作用，因为它可以在捕食者的胃肠道中引发有害的分泌过多以及明显的低血压。
