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[Mechanism of the decrease in free plasma calcium produced by the administration of inorganic phosphates]
Archivos Del Instituto De Cardiologia De Mexico
|November 1, 1981
Summary
Phosphate administration reduces free calcium levels, potentially explaining its antiarrhythmic effects in digitalis intoxication. Some added phosphates and calcium ions bind to plasma proteins, preventing precipitation.
Area of Science:
- Cardiology
- Biochemistry
- Pharmacology
Background:
- Previous research indicated sodium phosphates possess antiarrhythmic properties in digitalis intoxication.
- This effect was attributed to a reduction in the plasma free calcium fraction.
Purpose of the Study:
- To investigate the impact of varying phosphate concentrations on different calcium fractions.
- To elucidate the disposition of calcium ions removed from the plasma pool.
Main Methods:
- Digitalis intoxication models in intact dogs and heart-lung preparations.
- In vitro experiments using blood plasma exposed to different phosphate concentrations.
Main Results:
- Phosphate administration in intact dogs caused a slight decrease in total plasma and blood calcium.
- Increased phosphate levels correlated with significant reductions in free calcium.
- In heart-lung preparations, phosphates reduced free calcium but not total calcium.
- In vitro, elevated plasma phosphate linearly decreased free calcium without affecting total calcium.
- A portion of added phosphates and depleted calcium ions bound to plasma macromolecules, likely proteins, inhibiting precipitation.
Conclusions:
- Phosphate administration effectively lowers free calcium levels in various experimental models.
- Phosphate-induced hypocalcemia is primarily a reduction in free, not total, calcium.
- Plasma protein binding plays a role in the fate of phosphates and calcium ions, preventing precipitation.