Calcium Colorimetric Assay Kit (O-Cresolphthalein Method)

Calcium is the most abundant mineral, essential for all living organisms, where Ca²⁺ sequestration and release into and out of the cytoplasm functions as a signal for many cellular processes. 99% is present as calcium hydroxyapatite in bones and less than 1 % is present in the extra-osseous ICS (intracellular space) or ECS (extracellular space), responsible for a myriad of important physiological effects. Calcium ion channels control the migration of calcium ions across cell membranes, permitting the activation and inhibition of a wide variety of enzymes. Calcium ions affect the contractility of the heart and the skeletal musculature and are essential for the function of the nervous system. In addition, calcium ions play an important role in blood clotting and bone mineralization. Abnormal calcium levels have been tied to neurological, endocrine, cardiovascular, digestive, metabolic, and pulmonary diseases, as well as cancer. In plasma, calcium is bound to a considerable extent to proteins (approx. 40%), 10% is in the form of incorganic complexes and 50% is present as free (ionized) calcium. Clacium homeostasis is regulated by the parathyroid hormone (PTH), calcitriol (CT) and calcitonin. Low levels of calcium are found in hypoparathyroidism, pseudohypoparathyroidism, vitamin D deficiency, malnutrition and intestinal malabsorbtion.