Ilenwabor B P, Asowata E O, Obika L F
Department of Physiology, School of Basic Medical Sciences, University of Benin, Benin City, Edo State.
Niger J Physiol Sci. 2017 Jun 30;32(1):1-6.
The mineralocorticoid aldosterone is widely accepted as a key regulator of K+ balance as well as urinary K+excretion. However, recent evidence suggests that the circadian control of K+ excretion is independent of aldosterone. Thedelivery of Na+ to the distal nephron is known to be an important determinant of aldosterone mediated secretion of K+ in thissegment of the nephron. Examining the link between distal Na+ delivery and K+ excretion; and how this link affect circadianK+ excretion will advance what is currently known about the maintenance of K+ homeostasis. In the current study, weinvestigated the effect of furosemide-induced increase in distal tubular Na+ on K+ excretion. Na+, K+ and aldosterone levelswere measured in 12-hour day time and 12-hour night time urine samples following furosemide administration, andcompared with controls in 10 apparently healthy male subjects. To confirm the increased delivery of Na+ to the distal nephronby furosemide, increased Na+ excretion and aldosterone activity was observed in subjects administered furosemide.Consistent with previous reports, night time K+ excretion was significantly lower than day time, and this observation wasunchanged even with increased Na+ delivery to the distal tubules. In healthy individuals, aldosterone increases K+ secretionand this is known to further increase with increased Na+ delivery to the potassium secreting segment of the nephron. Eventhough the administration of furosemide increased aldosterone activity and the delivery of Na+ to the distal tubules, the dipin night time K+ excretion was unchanged. Our findings suggest that the circadian control of K+ excretion is not linked toNa+ levels and thus independent of aldosterone.
盐皮质激素醛固酮被广泛认为是钾平衡及尿钾排泄的关键调节因子。然而，最近有证据表明，钾排泄的昼夜节律控制独立于醛固酮。已知远端肾单位的钠输送是醛固酮介导该肾单位段钾分泌的重要决定因素。研究远端钠输送与钾排泄之间的联系，以及这种联系如何影响昼夜钾排泄，将推进目前对钾稳态维持的认识。在本研究中，我们调查了速尿诱导的远端肾小管钠增加对钾排泄的影响。在10名明显健康的男性受试者中，给予速尿后，在12小时白天和12小时夜间尿液样本中测量钠、钾和醛固酮水平，并与对照组进行比较。为了证实速尿增加了远端肾单位的钠输送，在给予速尿的受试者中观察到钠排泄和醛固酮活性增加。与之前的报道一致，夜间钾排泄明显低于白天，即使远端肾小管的钠输送增加，这一观察结果也没有改变。在健康个体中，醛固酮会增加钾分泌，并且已知随着钠输送到肾单位的钾分泌段增加，钾分泌会进一步增加。尽管给予速尿会增加醛固酮活性和远端肾小管的钠输送，但夜间钾排泄的下降没有改变。我们的研究结果表明，钾排泄的昼夜节律控制与钠水平无关，因此独立于醛固酮。
