Trinh-Trang-Tan M M, Bankir L, Doucet A, el Mernissi G, Imbert-Teboul M, Montégut M, Siaume S, Morel F
Pflugers Arch. 1985 Oct;405(3):216-22. doi: 10.1007/BF00582563.
The medullary thick ascending limb (MAL), but not the medullary collecting tubule (MCT), has been shown to have an impaired adenylate cyclase (AC) responsiveness to ADH and a selective hypoplasia in Brattleboro diabetes insipidus (DI) rats. Since chronic ADH administration has been found to increase epithelium volume and basolateral membrane surface area in MAL but not in MCT, we investigated whether chronic ADH infusion would affect the hormone-sensitive AC and the Na-K-ATPase activity--two markers of the basolateral membrane--in single micro-dissected portions of thick ascending limb and collecting tubule in DI rats. Results indicate that 1. in MAL of ADH-treated rats, AC responses to in vitro AVP and glucagon and Na-K-ATPase activity increased to the same extent as did epithelium volume (60-80%); 2. changes in the other segments were independent of any morphological alteration. In the cortical thick ascending limb, AVP and glucagon-sensitive AC decreased by 30-40% whereas Na-K-ATPase activity did not change. In the collecting tubule, AC response to in vitro AVP was not altered by ADH-treatment but glucagon-sensitive AC dropped by 50% and Na-K-ATPase activity doubled, independently of any variation in plasma aldosterone and glucagon levels. These results show that, in the MAL, the ADH-induced variations in enzyme activity are a reflection of the enlargement of the basolateral membrane surface area. Further studies are needed to clarify the origin of enzymatic alterations in the other segments.
髓质厚壁升支（MAL）而非髓质集合管（MCT），已被证明在布氏尿崩症（DI）大鼠中对血管加压素（ADH）的腺苷酸环化酶（AC）反应受损且存在选择性发育不全。由于已发现长期给予ADH可增加MAL而非MCT的上皮细胞体积和基底外侧膜表面积，我们研究了长期输注ADH是否会影响激素敏感的AC以及钠钾ATP酶活性（基底外侧膜的两个标志物），这两个指标来自DI大鼠的单个微解剖的厚壁升支和集合管部分。结果表明：1. 在接受ADH治疗的大鼠的MAL中，AC对体外抗利尿激素（AVP）和胰高血糖素的反应以及钠钾ATP酶活性增加的程度与上皮细胞体积相同（60 - 80%）；2. 其他节段的变化与任何形态学改变无关。在皮质厚壁升支中，AVP和胰高血糖素敏感的AC下降了30 - 40%，而钠钾ATP酶活性未改变。在集合管中，ADH治疗并未改变AC对体外AVP的反应，但胰高血糖素敏感的AC下降了50%，钠钾ATP酶活性增加了一倍，这与血浆醛固酮和胰高血糖素水平的任何变化无关。这些结果表明，在MAL中，ADH诱导的酶活性变化反映了基底外侧膜表面积的增大。需要进一步研究以阐明其他节段酶改变的起源。
