Sodium Imbalance in Mice Results Primarily in Compensatory Gene Regulatory Responses in Kidney and Colon, but Not in Taste Tissue

Abstract

Renal excretion and sodium appetite provide the basis for sodium homeostasis. In both the kidney and tongue, the epithelial sodium channel (ENaC) is involved in sodium uptake and sensing. The diuretic drug amiloride is known to block ENaC, producing a mild natriuresis. However, amiloride is further reported to induce salt appetite in rodents after prolonged exposure as well as bitter taste impressions in humans. To examine how dietary sodium content and amiloride impact on sodium appetite, mice were subjected to dietary salt and amiloride intervention and subsequently analyzed for ENaC expression and taste reactivity. We observed substantial changes of ENaC expression in the colon and kidney confirming the role of these tissues for sodium homeostasis, whereas effects on lingual ENaC expression and taste preferences were negligible. In comparison, prolonged exposure to amiloride-containing drinking water affected β- and αENaC expression in fungiform and posterior taste papillae, respectively, next to changes in salt taste. However, amiloride did not only change salt taste sensation but also perception of sucrose, glutamate, and citric acid, which might be explained by the fact that amiloride itself activates bitter taste receptors in mice. Accordingly, exposure to amiloride generally affects taste impression and should be evaluated with care.

Optogenetic Stimulation of Type I GAD65+Cells in Taste Buds Activates Gustatory Neurons and Drives Appetitive Licking Behavior in Sodium-Depleted Mice

“…We quantified drinking behaviors that were driven by NaCl taste and "light taste." As expected from previous studies (Caloiero and Lundy, 2004;Raymond et al, 2017;Lossow et al, 2020a), Na 1 depletion via amiloride selfadministration resulted in a robust NaCl appetite. Na 1 -depleted mice preferred to optogenetically stimulate GAD65 1 TBCs, which resulted in overconsumption of illuminated H 2 O, despite exacerbating their Na 1 imbalance in the process.…”

“…Each trial was repeated on the following day with the bottles reversed to account for any inherent side preference. The protocol was presented at the 2017 Association for Chemoreception Sciences Annual Meeting (Raymond et al, 2017) and was recently validated by others (Lossow et al, 2020a) as a rapid method for inducing Na 1 appetite.…”

Salt Taste, Nutrition, and Health

“…The authors suggest that "oral microbiota composition deserves to be considered as an influencing variable when investigating perireceptor events involved in chemosensory processes". Lossow et al [4] studied the effect of changes in dietary salt content on mRNA expression for ENaC subunits in mouse taste buds. They found that mRNA levels were not affected either by low-salt or by high-salt diet.…”

“…RAAS targets the renal nephron and the colon, where aldosterone affects sodium reabsorption through ENaC to match changes in sodium intake. Lossow et al [4] found that changes in dietary salt content in mice affected ENaC mRNA expression levels in kidney and distal colon. As reported above, they also analyzed ENaC expression in taste buds, since in this mammal ENaC works as sodium taste receptor.…”

Association between preeclampsia and prostasin polymorphism in Pakistani females

“…Although, sodium reabsorption by ENaC accounts for a comparatively small proportion (<5%), but it is the rate-limiting step and involved in final renal adjustment to sodium balance, ultimately regulating blood pressure. 8 Prostasin is believed to cause breakage of an inhibitory peptide from γ-ENaC in order to activate it intracellularly. 9 , 10 Studies on preeclamptic patients have also revealed that prostasin expression is present in the villi of primate and human placental cell lines.…”