title: The calcium ion activity and the standardized excretion rate of calcium in urine of healthy adults.
abstract: A standardized protocol is described for the study of the calcium excretion in urine. After 12 h of fasting, urine is collected during 4 h with a water load of 10 ml per kg body weight. Urine is also collected during the following 20 h period on the habitual water and calcium intake. Reference values for 48 healthy adults are given as 0.25 and 0.75 quantiles. The measured activity of calcium ions (Ca2+) in urine is 0.09-0.27 mmol/kg for the 4 h period, 0.34 to 0.52 mmol/kg for the 20 h period; pH values are 5.61-6.43 (4 h) and 5.46 to 6.04 (20 h). The concentrations of total calcium are 0.67-2.05 mmol/l (4 h) and 3.16 to 4.94 mmol/l (20 h). The value for the excretion rate of calcium (standardized to a creatinine clearance of 100 ml/min) is 1.30-3.24 mumol/min for the 4 h period and 3.06-4.88 mumol/min for the 20 h period, with no significant difference between the results for men and women. The relationship between the Ca2+ activity and pH was studied in urine titrated with HC1 or NaOH. In all urine the Ca2+ activity falls with increasing pH in a typical biphasic manner. This indicates the need for simultaneous measurement of the pH in order to interpret data for the Ca2+ activity in urine.
authors.forename: J
authors.initials: J
authors.lastname: Thode
mesh_terms: D000328:Adult; D000368:Aged; D002118:Calcium / Q000652:urine*; D000242:Cyclic AMP / Q000652:urine; D005215:Fasting; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008274:Magnesium / Q000032:analysis; D008297:Male; D008875:Middle Aged; D010710:Phosphates / Q000032:analysis; D012016:Reference Values; D014867:Water / Q000494:pharmacology
chemical_list: D010710:Phosphates; D014867:Water; D000242:Cyclic AMP; D008274:Magnesium; D002118:Calcium