Potassium transport though paracellular pathway in rat’s proximal tubules: the paper of claudins

• Grant number: 17/15203-5
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: September 01, 2017
• End date: August 31, 2018
• Field of knowledge: Biological Sciences - Physiology - Physiology of Organs and Systems
• Principal Investigator: Gerhard Malnic
• Grantee: Paloma Santos Monteiro
• Host Institution: Instituto de Ciências Biomédicas (ICB). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

Potassium is responsible for maintaining some of the basic functions of the cell, such as membrane potential. Its transport is executed by interactions between Na+/K+-ATPase and many other transport processes, which include channels for sodium and potassium, the paracellular path as well as cotransporters and counter-transporters of potassium. These processes are meant to avoid major disturbances in the plasma concentration, in order to guarantee the normal function of non-excitable and excitable tissues alike. The kidneys are responsible for the absorption and secretion of potassium along the renal tubules, processes driven by specific transport mechanisms. In this sense, we intend to evaluate mechanisms of potassium transport through the technique of renal tubule microperfusion, particularly from the blood to urine, or, in other words, from the lumen to peritubular capillaries. Claudins are proteins necessary for the formation of intercellular junctions, leaky and tight, seal epithelial to each other, which are responsible for regulation of the paracellular path for water and solutes. These junctions, leaky for proximal tubule, are composed of a long follow-up of adhesion proteins, being the claudins being an important protein of the junctions. Although the literature describes an existence of 24 claudin isoforms, its exact mechanism function is not well known. We hope, with this project, to identify the role of claudin isoform 2 (CLDN2) in the regulation of potassium reabsorption in the proximal tubule. Since this project will evaluate mechanisms of transfer of potassium across the proximal tubule epithelium, we plan to use ouabain, which has been shown to, besides its action on Na-K ATPase, also block the passage of ions across the paracellular pathway. In this way, we plan to obtain new information on potassium transfer from lumen to blood in proximal tubule epithelium. (AU)