Impact of vasopressin on cell‐autonomous expression of membrane transport proteins in rat distal nephron

Abstract

Transcellular reabsorption of NaCl in kidney thick ascending limb (TAL) is controlled by Na,K,2Cl cotransporter (NKCC2) and involves the action of luminal (ROMK) and basolateral (Kir4.1) potassium channels, a basolateral calcium sensing receptor (CaSR); paracellular transport controlled by the claudin family of proteins. A morphological cell heterogeneity has previously been described, and mosaic expression of ROMK and Kir4.1 was reported. Here we have studied TAL EM morphology and zonal as well as cell‐autonomous heterogeneity of the transport proteins at steady state and under stimulation by vasopressin (AVP; V2R agonist dDAVP for 7 or 72 h) using AVP‐deficient Brattleboro (BB) and Long Evans (LE) control rats. NKCC2, ROMK, Kir4.1, CaSR, and Claudin (Cldn)‐10 and ‐16 signals were analyzed using immunohistochemistry, in situ hybridization, EM and Western blot (WB).TAL morphological cell heterogeneity was obvious between kidney zones, but not at the cell‐to‐cell level within a zone. NKCC2 was continuously expressed in all TAL cells throughout, whereas ROMK vs. CaSR and Kir4.1 expression showed conspicous heterogeneity in a mutually exclusive pattern. Nearly all tight junctions (TJ) of inner stripe TAL were Cldn‐10 positive. In the outermost inner stripe and outer stripe, Cldn‐10‐ and ‐16 signals were coexpressed; ROMK‐positive cells had Cld‐10‐positive TJ, whereas ROMK‐negative cells had Cldn‐16‐positive TJ. 72h dDAVP administration significantly increased the number of ROMK‐positive cells which then coexpressed Kir4.1 signal. In parallel, Cldn‐10 expressing TJ became more numerous at the expense of Cldn‐16‐positive TJ. WB analysis showed 2.2‐fold increase for ROMK, 1.3‐fold for Kir4.1, but down‐regulation for CaSR to 60%. ISH revealed no differences in mRNA abundances. No significant changes were detected after 7h.The present results demonstrate expressional cell heterogeneity in TAL with respect to individual cell ROMK, Kir4.1, CaSR, and Cldn‐10 and ‐16 signals and reflect an AVP‐dependent adaptive mechanism in renal solute handling in the outer medulla.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.