Chemical formula: CaClâ‚‚ Molecular mass: 110.984 g/mol PubChem compound: 5284359
Calcium is the most abundant mineral in the body, and is an essential body electrolyte. Homeostasis is mainly regulated by the parathyroid hormone, by calcitonin, and by the activated form of vitamin D.
Parathyroid hormone is released when the calcium blood level is low. It stimulates osteoclasts to release calcium into the blood, and increases the absorption of calcium from the gastrointestinal tract.
Calcitonin, from the thyroid gland, decreases the blood level of calcium by stimulating osteoblasts and inhibiting osteoclasts. In the presence of calcitonin, osteoblasts remove calcium from the blood and deposit it in the bone.
Calcium is a structural component of bones and teeth. It is also required for blood clotting, neurotransmitter release, muscle contraction and normal heartbeat.
Calcium ions increase the force of myocardial contraction. In response to electrical stimulation of muscle, calcium ions enter the sarcoplasm from the extracellular space. Calcium ions contained in the sarcoplasmic reticulum are rapidly transferred to the sites of interaction between the actin and myosin filaments of the sarcomere to initiate myofibril shortening. Thus, calcium increases myocardial function. Calcium’s positive inotropic effects are modulated by its action on systemic vascular resistance. Calcium may either increase or decrease systemic vascular resistance. In the normal heart, calcium’s positive inotropic and vasoconstricting effect produces a predictable rise in systemic arterial pressure.
The body contains about 1200g of calcium (or 300 to 500 mmol per Kg body weight), approximately 99% of which is found in the skeleton. The normal concentration of calcium in plasma is between 2.15 to 2.60 mmol per litre.
Calcium is absorbed from the small intestine. The amount of calcium absorbed varies depending on several factors including the requirements of the body, but is normally only about 30% of the dietary intake.
The absorption of calcium is increased during periods of high physiological requirement such as during pregnancy and lactation.
The amount of dietary calcium required by an adult is about 700 to 800 mg (17.5-20 mmol) per day.
After absorption calcium is eventually incorporated into bones and teeth with 99% of the body’s calcium content being present in such skeletal tissue. The remaining calcium is present in both the intra- and extracellular fluids.
About 50% of the total blood-calcium content is in the physiologically active ionised form with 5% being complexed to citrate, phosphate or other anions and 45% being bound to proteins.
Excretion of calcium occurs in the urine although a large proportion is reabsorbed in the renal tubules. Excretion also occurs in the faeces, this consisting of unabsorbed calcium as well as that secreted in the bile and pancreatic juice. Minor amounts are lost in the sweat. Calcium crosses the placenta and is also excreted in breast milk.
Calcium chloride has been used for many years and has a proven safety record. No pre-clinical safety data is supplied.
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