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Calcium uptake by placental plasma membrane vesicles.
Biochimica Et Biophysica Acta
|August 20, 1975
Summary
Placental plasma membrane vesicles efficiently accumulate calcium (Ca2+), a process powered by ATP hydrolysis via the placental Ca2+-ATPase. Phosphate significantly enhances this Ca2+ uptake, particularly at higher concentrations.
Area of Science:
- Biochemistry
- Cell Biology
- Physiology
Background:
- The placenta plays a crucial role in nutrient transport, including calcium (Ca2+).
- Understanding the mechanisms of Ca2+ transport across the placental barrier is vital for fetal development.
Purpose of the Study:
- To investigate the capacity and regulation of Ca2+ accumulation by placental plasma membrane vesicles.
- To elucidate the role of placental Ca2+-ATPase in active Ca2+ transport.
Main Methods:
- Isolation of placental plasma membrane vesicles.
- Measurement of Ca2+ uptake in the presence of ATP.
- Assessment of the effects of phosphate (Pi) and magnesium (Mg2+) on Ca2+ accumulation.
Main Results:
- Placental vesicles accumulated Ca2+ to concentrations 24-fold higher than external levels.
- Ca2+ uptake was dependent on ATP hydrolysis by the placental Ca2+-ATPase.
- Phosphate significantly enhanced Ca2+ uptake, doubling it at 5 mM Ca2+.
- Mg2+ enhanced Ca2+ uptake only at low external Ca2+ concentrations.
Conclusions:
- Placental plasma membrane vesicles possess a high capacity for active Ca2+ transport.
- Placental Ca2+-ATPase is the primary driver of this active Ca2+ accumulation.
- Phosphate acts as a significant modulator of placental Ca2+ uptake, suggesting a complex regulatory mechanism.