Gona O
J Endocrinol. 1982 Apr;93(1):133-8. doi: 10.1677/joe.0.0930133.
The uptake of 125I-labelled ovine prolactin in the bullfrog kidney was studied by autoradiography. Five minutes after the intracardiac injection of 125I-labelled prolactin, no labelling was detected in the kidneys of premetamorphic tadpoles or in animals whose forelimbs had just emerged (climax tadpoles). After 15 min, a few isolated tubules were labelled in the premetamorphic tadpole kidneys and many kidney tubules were labelled in climax tadpoles. In the froglet kidneys, extensive labelling was seen by 5 min after injection, and only distal tubules seemed to be consistently unlabelled. The radioactive label was displaced by an excess of unlabelled ovine prolactin, but not by ovine growth hormone or bovine LH. These findings provide the first morphological demonstration of specific binding of prolactin by the nephric tubules of an amphibian. They show that the receptors, present in small numbers in the premetamorphic state, proliferate during the later stages of metamorphosis. The change in receptor density involves both an increase in the number of tubules having receptors and in the density of receptors per tubule.
通过放射自显影术研究了牛蛙肾脏对125I标记的绵羊催乳素的摄取情况。在心内注射125I标记的催乳素5分钟后，在变态前蝌蚪或前肢刚出现的动物（变态高峰期蝌蚪）的肾脏中未检测到标记。15分钟后，变态前蝌蚪的肾脏中有一些孤立的肾小管被标记，变态高峰期蝌蚪的许多肾小管被标记。在幼蛙肾脏中，注射后5分钟可见广泛的标记，只有远端肾小管似乎始终未被标记。放射性标记被过量的未标记绵羊催乳素取代，但未被绵羊生长激素或牛促黄体生成素取代。这些发现首次从形态学上证明了两栖动物肾小管对催乳素的特异性结合。它们表明，在变态前状态下数量较少的受体在变态后期会增殖。受体密度的变化涉及有受体的肾小管数量增加以及每个肾小管中受体密度增加。
