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Hydrogen sulfide consumption measured at low steady state concentrations using a sulfidostat
Dennis G Searcy1, Michael A Peterson
1Biology Department, University of Massachusetts, Amherst, MA 01003, USA. dsearcy@bio.umass.edu
Analytical Biochemistry
|December 24, 2003
Summary
Researchers developed a Sulfidostat to measure low-concentration sulfide consumption in cells. This new apparatus enables precise measurement of hydrogen sulfide (H2S) uptake, revealing higher rates than previously observed.
Area of Science:
- Biochemistry
- Environmental Science
- Cell Biology
Background:
- Hydrogen sulfide (H2S) at concentrations above 10 microM is toxic to eukaryotic cells.
- However, H2S at concentrations below 1 microM is rapidly consumed and oxidized by cells.
- Measuring this low-concentration sulfide consumption is crucial for understanding cellular H2S metabolism.
Purpose of the Study:
- To develop and validate a novel apparatus, the Sulfidostat, for accurately measuring sulfide consumption at micromolar and sub-micromolar concentrations.
- To quantify the rate of sulfide consumption in the protozoan Tetrahymena pyriformis at low H2S concentrations.
- To compare H2S consumption rates measured by the Sulfidostat with those determined by traditional methods.
Main Methods:
- Construction of a Sulfidostat apparatus utilizing a sulfide-specific electrode linked to a computer-controlled syringe pump.
- Validation of the sulfide electrode's response to low sulfide concentrations at neutral pH.
- Measurement of sulfide consumption rates by determining the injection rate of Na2S solution required to maintain a constant sulfide concentration in the presence of Tetrahymena pyriformis.
Main Results:
- The Sulfidostat successfully measured sulfide consumption at concentrations below 1 microM.
- Maximum sulfide consumption in Tetrahymena pyriformis was observed around 0.5 microM sulfide.
- The maximum consumption rate was measured at 250 nmol (g protein)(-1) s(-1), which is higher than previously calculated rates.
Conclusions:
- The Sulfidostat is an effective tool for measuring low-concentration sulfide consumption, overcoming limitations of previous methods.
- The observed higher consumption rates can be attributed to the Sulfidostat's continuous measurement and potential underestimation by bolus addition methods due to electrode response time and reversible cell binding.
- This technology opens new avenues for studying cellular sulfide metabolism and its physiological implications.
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