Test Page: Difference between revisions

The answer is C. Plasma Ca2+ is maintained at a concentration of 9 to 10.5 g/dL (2.2 to 2.4 mmol/L) as total calcium, with approximately 40% of this value comprising the protein-bound nonfiltratable fraction, and 10% is chelated. Ionized calcium accounts for 47% of the total circulating Ca2+ and ranges from 4 to 5 mg/dL (1.0 to 1.25 mmol/L) <ref>J Clin Invest. 1970;49(2):318–334[http://www.jci.org/articles/view/106241]</ref>. The extent of protein binding per deciliter of plasma is approximately 0.8 mg of Ca2+ for every 1 g of albumin and 0.16 mg for each 1 g of globulin. Furthermore, a threefold increase in serum phosphate or sulfate concentration results in a 10% decrease in serum Ca2+ concentration. In addition, the binding of Ca2+ to albumin is pH-dependent between pH 7 and 9. An acute increase or decrease in the pH by 0.1 units results in an increase or a decrease, respectively, of proteinbound Ca2+ of 0.2 mg/dL (0.05 mmol/L).<ref>JASN July 2008 vol. 19 no. 7 1257-1260 [http://jasn.asnjournals.org/content/19/7/1257.full]</ref>