Falkenstein D, Ribeiro C A, Figueiredo J F
Departamento de Fisiologia e Biofísica, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, SP, Brasil.
Braz J Med Biol Res. 1999 Aug;32(8):1045-9. doi: 10.1590/s0100-879x1999000800016.
High magnesium concentration inhibits the effect of arginine vasopressin (AVP) on smooth muscle contraction and platelet aggregation and also influences hepatocyte AVP receptor binding. The aim of this study was to determine the role of magnesium concentration [Mg2+] in AVP-stimulated water transport in the kidney collecting duct. The effect of low and high peritubular [Mg2+] on the AVP-stimulated osmotic water permeability coefficient (Pf) was evaluated in the isolated perfused rabbit cortical collecting duct (CCD). Control tubules bathed and perfused with standard Ringer bicarbonate solution containing 1 mM Mg2+ presented a Pf of 223.9 +/- 27.2 microm/s. When Mg2+ was not added to the bathing solution, an increase in the AVP-stimulated Pf to 363.1 +/- 57.2 microm/s (P<0. 05) was observed. An elevation of Mg2+ to 5 mM resulted in a decrease in Pf to 202.9 +/- 12.6 microm/s (P<0.05). This decrease in the AVP-stimulated Pf at 5 mM Mg2+ persisted when the CCDs were returned to 1 mM Mg2+, Pf = 130.2 +/- 20.3 microm/s, and was not normalized by the addition of 8-[4-chlorophenylthio]-adenosine 3', 5'-cyclic monophosphate, a cAMP analogue, to the preparation. These data indicate that magnesium may play a modulatory role in the action of AVP on CCD osmotic water permeability, as observed in other tissues.
高镁浓度会抑制精氨酸加压素（AVP）对平滑肌收缩和血小板聚集的作用，还会影响肝细胞AVP受体结合。本研究的目的是确定镁浓度[Mg2+]在AVP刺激的肾集合管水转运中的作用。在离体灌注的兔皮质集合管（CCD）中评估了低管周[Mg2+]和高管周[Mg2+]对AVP刺激的渗透水渗透系数（Pf）的影响。用含1 mM Mg2+的标准林格碳酸氢盐溶液进行浴灌流的对照小管，其Pf为223.9±27.2微米/秒。当浴液中不添加Mg2+时，观察到AVP刺激的Pf增加至363.1±57.2微米/秒（P<0.05）。将Mg2+升高至5 mM导致Pf降低至202.9±12.6微米/秒（P<0.05）。当CCD恢复到1 mM Mg2+时，5 mM Mg2+时AVP刺激的Pf降低持续存在，Pf = 130.2±20.3微米/秒，并且通过向制剂中添加8-[4-氯苯硫基]-腺苷3'，5'-环磷酸单酯（一种cAMP类似物）未使其恢复正常。这些数据表明，镁可能在AVP对CCD渗透水通透性的作用中起调节作用，正如在其他组织中观察到的那样。
