# Molecular Mechanisms Regulating Ammonia Metabolism

> **NIH NIH R01** · UNIVERSITY OF FLORIDA · 2023 · $335,500

## Abstract

Project Summary/Abstract
 The renal maintenance of acid-base homeostasis is critical for optimal health. Collecting duct intercalated
cells play a central role in this process through adaptive changes in proton secretion, bicarbonate secretion, and
Rh glycoproteins-mediated ammonia transport. Our current paradigm is that the primary determinant of this
response involves direct effects of extracellular pH on intercalated cells.
 We suggest a new paradigm. Deletion of the proximal tubule-specific basolateral bicarbonate
transporter, NBCe1-A, causes severe metabolic acidosis, yet inhibits intercalated cell phenotypic characteristics
of acid secretion and inhibits the intercalated cell plasticity response to acid-loading. This is not an off-target
effect of the TALEN gene-editing procedure; identical effects were seen with NBCe1-A/B deletion generated
using Cre-lox techniques. Published work shows that the K+ disorders, hypokalemia and hyperkalemia, alter
intercalated cell phenotype and plasticity in a pattern which cannot be explained by extracellular pH. The effects
of NBCe1-A or NBCe1-A/B deletion, or of K+ disorders likely involve ammonia. Each alters proximal tubule-
derived ammonia generation in a pattern which parallels the observed intercalated cell responses. Isolated
perfused collecting duct studies show ammonia acutely and directly regulates intercalated cell H⁺ and
bicarbonate transport. Thus, we propose a new paradigm, that proximal tubule-derived ammonia, which is
concentrated in the renal interstitium by the TAL, is a primary determinant of intercalated cell phenotypic
characteristics and plasticity response. Our proposed studies investigate this new paradigm in detail.
 Specific Aim 1 will determine the effect of gene deletion maneuvers which directly and specifically alter
proximal tubule and thick ascending limb ammonia metabolism on intercalated cell phenotype and plasticity. We
will use a combination of gene deletion approaches, including proximal tubule-specific deletion of PDG, the initial
and the rate-limiting enzyme in ammoniagenesis, and TAL NHE4 deletion, which directly impacts ammonia
concentration into the renal interstitium where we propose it regulates intercalated cells. We will study the effect
of these gene deletion so in a variety of conditions, including basal state, acid-loading, and abnormal potassium
homeostasis, both hypokalemia and hyperkalemia.
 Specific Aim 2 will determine the signaling mechanisms through which proximal tubule regulates
intercalated cell phenotypic characteristics and plasticity. We will identify whether this is direct stimulator of
pathways or acts parallel to and independent of signaling pathways known to alter intercalated cells, including
GDF15, hensin, GPR4, and SDF1.
 These studies will substantially advance our understanding of the molecular mechanisms regulating
thereby acid-base homeostasis.

## Key facts

- **NIH application ID:** 10694020
- **Project number:** 5R01DK107798-08
- **Recipient organization:** UNIVERSITY OF FLORIDA
- **Principal Investigator:** I. David Weiner
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2023
- **Award amount:** $335,500
- **Award type:** 5
- **Project period:** 2015-12-15 → 2026-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10694020

## Citation

> US National Institutes of Health, RePORTER application 10694020, Molecular Mechanisms Regulating Ammonia Metabolism (5R01DK107798-08). Retrieved via AI Analytics 2026-05-21 from https://api.ai-analytics.org/grant/nih/10694020. Licensed CC0.

---

*[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*