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Polymyxin B sulfate-induced pH-dependent increase in calcium influx in cultured fibroblasts
Abstract:
Polymyxin B sulfate treatment induced an increase in calcium influx in mouse fibroblasts (3T6) and normal human skin fibroblasts. This increase in calcium influx occurred in a dose- and time-dependent fashion and was dependent on pH but independent of the electrochemical gradient of calcium across the plasma membrane. This effect was prevented when cycloheximide (20 micrograms/ml) was added with polymyxin B sulfate. Addition of actinomycin D (2 micrograms/ml) also remarkably reduced this effect. In view of these findings, it is possible that polymyxin B sulfate therapy-induced side effects, such as neuromuscular blockade and kidney dysfunction, are conditional and may be due to an increase in calcium influx.
Insights
Polymyxin B sulfate increases calcium influx in cells, potentially explaining side effects like neuromuscular blockade and kidney dysfunction. This cellular effect is dose- and time-dependent and requires protein synthesis.
Area of Science:
- Cell Biology
- Pharmacology
Background:
- Polymyxin B sulfate is an antibiotic used to treat infections.
- The precise mechanisms underlying Polymyxin B sulfate's side effects remain incompletely understood.
Purpose of the Study:
- To investigate the effect of Polymyxin B sulfate on calcium influx in mammalian fibroblasts.
- To explore the potential link between altered calcium influx and Polymyxin B sulfate-induced toxicity.
Main Methods:
- Primary mouse fibroblasts (3T6) and normal human skin fibroblasts were treated with varying concentrations of Polymyxin B sulfate.
- Calcium influx was measured using standard assays.
- The role of protein synthesis was assessed by co-administering cycloheximide or actinomycin D.
Main Results:
- Polymyxin B sulfate treatment significantly increased calcium influx in both cell types in a dose- and time-dependent manner.
- The observed increase in calcium influx was dependent on extracellular pH but not on the electrochemical gradient of calcium.
- Inhibition of protein synthesis with cycloheximide or actinomycin D markedly reduced the effect of Polymyxin B sulfate on calcium influx.
Conclusions:
- Polymyxin B sulfate induces an increase in intracellular calcium levels in fibroblasts.
- This mechanism, dependent on protein synthesis, may contribute to the known side effects of Polymyxin B sulfate therapy, including neuromuscular blockade and nephrotoxicity.