Mandon B, Siga E, Chabardes D, Firsov D, Roinel N, De Rouffignac C
Département de Biologie Cellulaire et Moléculaire, Centre d'Etudes Nucléaires de Saclay, Commissariat à l'Energie Atomique, Gif sur Yvette, France.
Am J Physiol. 1993 Sep;265(3 Pt 2):F361-9. doi: 10.1152/ajprenal.1993.265.3.F361.
Insulin (Ins) decreases Na+ delivery in the final urine. To determine whether the loop of Henle participates in this reduction, the effects of Ins were tested on cortical (CTAL) and medullary thick ascending limbs (MTAL) of the mouse nephron, microperfused in vitro. In the MTAL, Ins increased the transepithelial potential difference (Vt) and the Na+ and Cl- net reabsorption fluxes (JNa and JCl, respectively) in a dose-dependent manner, the threshold being below 10(-9) M. At 10(-7) M, Ins reversibly increased JNa and JCl, leaving Mg2+ and Ca2+ fluxes (JMg and JCa, respectively) close to zero. In the CTAL, 10(-7) M Ins reversibly increased Vt, JNa, JCl, JMg, and JCa. In CTAL segments perfused under asymmetrical conditions, with a bath-to-lumen-directed NaCl gradient (lumen 50 mM NaCl, bath 150 mM NaCl), addition of 10(-7) M Ins to the bath resulted in a large increase in JMg and JCa. Thus the responses of CTAL and MTAL to Ins are in all ways similar to those already reported for the adenosine 3',5'-cyclic monophosphate (cAMP)-generating hormones acting on these nephron segments. When 10(-10) M arginine vasopressin (AVP) and 10(-7) M Ins were used in combination, previous addition of one hormone to the bath potentiated the response to the second hormone. In cAMP accumulation experiments, performed in the presence of a phosphodiesterase inhibitor, the amounts of cAMP formed with 10(-7) M Ins and 10(-10) M AVP (which elicit maximal physiological responses in these segments) were in the same range.(ABSTRACT TRUNCATED AT 250 WORDS)
胰岛素（Ins）可减少终尿中的钠离子排泄。为确定髓袢是否参与了这种减少过程，研究了Ins对体外微量灌注的小鼠肾单位皮质厚升支（CTAL）和髓质厚升支（MTAL）的影响。在MTAL中，Ins以剂量依赖方式增加跨上皮电位差（Vt）以及钠离子和氯离子的净重吸收通量（分别为JNa和JCl），阈值低于10⁻⁹ M。在10⁻⁷ M时，Ins可逆性增加JNa和JCl，使镁离子和钙离子通量（分别为JMg和JCa）接近零。在CTAL中，10⁻⁷ M Ins可逆性增加Vt、JNa、JCl、JMg和JCa。在不对称条件下灌注的CTAL节段中，浴液与管腔之间存在由浴液指向管腔的氯化钠梯度（管腔50 mM氯化钠，浴液150 mM氯化钠），向浴液中添加10⁻⁷ M Ins会导致JMg和JCa大幅增加。因此，CTAL和MTAL对Ins的反应在各方面都与已报道的作用于这些肾单位节段的能产生3',5'-环磷酸腺苷（cAMP）的激素的反应相似。当联合使用10⁻¹⁰ M精氨酸加压素（AVP）和10⁻⁷ M Ins时，预先向浴液中添加一种激素会增强对第二种激素的反应。在存在磷酸二酯酶抑制剂的情况下进行的cAMP积累实验中，10⁻⁷ M Ins和10⁻¹⁰ M AVP（在这些节段中引发最大生理反应）所形成的cAMP量在同一范围内。（摘要截短于250词）
