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Updated: Aug 16, 2026
Isolation, Characterization, And High Throughput Extracellular Flux Analysis of Mouse Primary Renal Tubular Epithelial Cells
Published on: June 20, 2018
Media acidification inhibits TGF beta-mediated growth suppression in cultured rabbit proximal tubule cells
D Tovbin1, H A Franch, R J Alpern
1Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas 75235-8856, USA.
Abstract:
Chronic metabolic acidosis induces both hyperplastic and hypertrophic renal growth and is associated with progressive loss of renal function. These studies examine the direct effect of media acidification on the growth of rabbit proximal tubule cells in primary culture. The results demonstrate that media acidification has a direct antiproliferative (hypoplastic) effect on both quiescent and mitogen-stimulated [epidermal growth factor (EGF)-stimulated] cells and does not induce hypertrophy. This direct antiproliferative effect of acid is associated with inhibition of EGF-induced phosphorylation of the retinoblastoma protein (pRB), which maintains pRB activity and inhibits cell cycle progression from G1 to S phase. Transforming growth factor-beta (TGF-beta) alone has an antiproliferative effect in these cells. TGF-beta converts EGF-induced hyperplasia to hypertrophy and inhibits EGF-induced pRB phosphorylation. Media acidification inhibits both the antiproliferative effect of TGF-beta and the ability of TGF-beta to convert EGF-induced hyperplasia to hypertrophy. This activity is associated with inhibition of TGF-beta-mediated retention of pRB in the active, hypophosphorylated state. These results demonstrate that metabolic acidosis has a direct growth-suppressive effect on renal epithelial cells but inhibits the growth-suppressive effects of TGF-beta. Inhibition of the antiproliferative effect of cytokines, such as TGF-beta, may be responsible for acidosis-induced hyperplasia in vivo.
Insights
Metabolic acidosis directly suppresses renal epithelial cell growth, inhibiting cell cycle progression. However, it also counteracts the growth-inhibitory effects of transforming growth factor-beta (TGF-beta), potentially explaining acidosis-induced kidney hyperplasia.
Area of Science:
- Nephrology
- Cell Biology
- Molecular Biology
Background:
- Chronic metabolic acidosis is linked to renal dysfunction and altered kidney growth.
- Understanding the direct cellular effects of acidosis on kidney cells is crucial for explaining in vivo observations.
Purpose of the Study:
- To investigate the direct impact of media acidification on rabbit proximal tubule cell growth.
- To elucidate the molecular mechanisms underlying the effects of acidosis and growth factors on cell proliferation and cell cycle regulation.
Main Methods:
- Primary culture of rabbit proximal tubule cells.
- Stimulation with epidermal growth factor (EGF) and transforming growth factor-beta (TGF-beta).
- Analysis of retinoblastoma protein (pRB) phosphorylation status.
Main Results:
- Media acidification directly inhibits cell proliferation (hypoplasia) in both quiescent and EGF-stimulated cells.
- Acidification inhibits EGF-induced phosphorylation of retinoblastoma protein (pRB), maintaining its active state and blocking cell cycle progression.
- Acidification blocks the antiproliferative effects of TGF-beta and its ability to convert EGF-induced hyperplasia to hypertrophy.
- Acidification interferes with TGF-beta-mediated retention of pRB in its hypophosphorylated state.
Conclusions:
- Metabolic acidosis exerts a direct growth-suppressive effect on renal epithelial cells.
- Acidosis inhibits the growth-suppressive actions of TGF-beta, potentially leading to hyperplasia in vivo.
- The interplay between acidosis, growth factors, and pRB regulation is key to understanding acidosis-induced renal growth changes.
