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Updated: Jun 28, 2026
Analyses of Mitochondrial Calcium Influx in Isolated Mitochondria and Cultured Cells
Published on: April 27, 2018
Mitochondrial inhibitors activate influx of external Ca(2+) in sea urchin sperm
F Ardón1, E Rodríguez-Miranda, C Beltrán
1Departamento de Biofísica, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Distrito Federal, 04510, México.
Abstract:
Sea urchin sperm have a single mitochondrion which, aside from its main ATP generating function, may regulate motility, intracellular Ca(2+) concentration ([Ca(2+)](i)) and possibly the acrosome reaction (AR). We have found that acute application of agents that inhibit mitochondrial function via differing mechanisms (CCCP, a proton gradient uncoupler, antimycin, a respiratory chain inhibitor, oligomycin, a mitochondrial ATPase inhibitor and CGP37157, a Na(+)/Ca(2+) exchange inhibitor) increases [Ca(2+)](i) with at least two differing profiles. These increases depend on the presence of extracellular Ca(2+), which indicates they involve Ca(2+) uptake and not only mitochondrial Ca(2+) release. The plasma membrane permeation pathways activated by the mitochondrial inhibitors are permeable to Mn(2+). Store-operated Ca(2+) channel (SOC) blockers (Ni(2+), SKF96365 and Gd(2+)) and internal-store ATPase inhibitors (thapsigargin and bisphenol) antagonize Ca(2+) influx induced by the mitochondrial inhibitors. The results indicate that the functional status of the sea urchin sperm mitochondrion regulates Ca(2+) entry through SOCs. As neither CCCP nor dicycloexyl carbodiimide (DCCD), another mitochondrial ATPase inhibitor, eliminate the oligomycin induced increase in [Ca(2+)](i), apparently oligomycin also has an extra mitochondrial target.
Insights
Mitochondrial inhibitors in sea urchin sperm increase intracellular calcium (Ca2+) by activating store-operated calcium channels (SOCs). This finding reveals a novel regulatory role for sperm mitochondria in controlling calcium influx.
Area of Science:
- Spermatology
- Mitochondrial Physiology
- Calcium Signaling
Background:
- Sea urchin sperm mitochondria play roles beyond ATP production, potentially regulating motility, intracellular calcium ([Ca2+]i), and acrosome reaction (AR).
- Understanding how mitochondrial function impacts sperm physiology is crucial for reproductive biology.
Purpose of the Study:
- To investigate the role of sea urchin sperm mitochondria in regulating intracellular calcium concentration ([Ca2+]i).
- To determine the mechanisms by which mitochondrial inhibitors affect Ca2+ influx in sperm.
Main Methods:
- Acute application of various mitochondrial inhibitors (CCCP, antimycin, oligomycin, CGP37157) to sea urchin sperm.
- Measurement of intracellular Ca2+ concentration ([Ca2+]i) changes.
- Assessment of Ca2+ influx dependency on extracellular Ca2+ and permeability to Mn2+.
- Use of store-operated Ca2+ channel (SOC) blockers and internal-store ATPase inhibitors (Ni2+, SKF96365, Gd2+, thapsigargin, bisphenol) to antagonize Ca2+ influx.
Main Results:
- Inhibition of mitochondrial function by diverse agents significantly increased [Ca2+]i in a manner dependent on extracellular Ca2+.
- The activated plasma membrane pathways were permeable to Mn2+, indicating Ca2+ uptake.
- SOC blockers and internal-store ATPase inhibitors effectively antagonized the Ca2+ influx induced by mitochondrial inhibitors.
- Oligomycin-induced [Ca2+]i increase was not fully abolished by other mitochondrial inhibitors, suggesting an additional extramitochondrial target for oligomycin.
Conclusions:
- The functional state of sea urchin sperm mitochondria is a key regulator of Ca2+ entry through store-operated calcium channels (SOCs).
- Mitochondrial inhibitors trigger Ca2+ influx via SOCs, highlighting an indirect mechanism of calcium regulation.
- Oligomycin may possess extramitochondrial targets influencing Ca2+ homeostasis in sperm.
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