Background: Basolateral Kir4.1/Kir5.1 in the DCT plays a key role in mediating the effect of dietary K + intake on NCC expression/activity through Cl--sensitive with-no-lysine kinase which stimulates ste20-proline-alanine rich kinase. While Kir4.1/Kir5.1 heterotetramer is expressed in both early DCT (DCT1) and late DCT (DCT2), DCT1 and DCT2 have two distinguished membrane transport properties. Previous study demonstrated that overnight sodium restriction stimulated Kir4.1/Kir5.1 first in DCT2, an effect depends on the presence of AT1aR. This raises the question whether overnight dietary K + changes also regulate Kirr4.1/Kir5.1 differently between DCT1 and DCT2. Hypothesis: The aim of the present study is to test the hypothesis that dietary K + intake-induced regulation of basolateral Kir4.1/Kir5.1 is different between DCT1 and DCT2. Methods: We used immunoblotting to examine the expression of NCC and performed the patch-clamp experiments to examine Kir4.1/Kir5.1 activity in DCT1 and DCT2 in male/female AT1aR-floxed mice (wild-type) and kidney-tubule-specific AT1aR-Knockout mice (Ks-AT1aR-KO) on overnight high-K + (HK) and overnight low-K + (LK), respectively. Results: We used the perforated whole-cell recording to measure Ba2+-sensitive K + currents in DCT1 and DCT2. Since DCT1 lacks functional ROMK, the whole-cell K + current is equal to Kir4.1/Kir5.1. In contrast, because ROMK is active in DCT2, we inhibited ROMK currents by adding 400 nM TPNQ into a split-open DCT2 for the measurement of TPNQ-insensitive and Ba2+-sensitive Kir4.1/Kir5.1-mediated K + currents (equal to Kir4.1/Kir5.1 activity). We first examined the effect of overnight-LK intake on the basolateral Kir4/1/Kir5.1 activity in the DCT1 and DCT2. Overnight LK intake significantly increased Kir4.1/Kir5.1 currents in DCT1 in comparison to NK. In contrast, overnight LK did not stimulate Kir4.1/Kir5.1 in DCT2. Western blots showed that overnight LK intake increased abundance of p(Thr53)-NCC (pNCC) and total NCC (tNCC) in both m/f mice. We next examined the effect of overnight HK-intake on the basolateral Kir4/1/Kir5.1 activity in DCT1 and DCT2. Overnight HK intake significantly decreased Kir4.1/Kir5.1 currents in DCT1 in comparison to NK. In contrast, overnight HK did not stimulate Kir4.1/Kir5.1 in DCT2. Moreover, deletion of AT1aR in the renal tubule did not affect the effect of dietary K + intake on the basolateral Kir4.1/Kir5.1. Overnight-LK still predominantly increased Kir4.1/Kir5.1 activity in DCT1 whereas overnight-HK intake predominantly inhibited Kir4.1/Kir5.1 in the DCT1 of AT1aR-knockout mice. Conclusion: Overnight dietary K + -induced regulation of Kir4.1/Kir5.1 is initiated predominantly in the early DCT and deletion of AT1aR had no effect on dietary K intake-induced regulation of Kir4.1/Kir5.1. This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.
Duan et al. (Fri,) studied this question.