PLASMA CALCIUM FRACTIONS IN NORMAL SUBJECTS FROM BIRTH TO ADULT AGES

A simple and rapid method to determine ultra-filtrable calcium in plasma is described in detail. Total calcium, ultrafiltrable calcium (Ca_uf), and protein-bound calcium in plasma are reported for 202 normal children (range 0–16 years of age) divided into 12 age groups, as well as for 93 healthy male blood donors. There was a decrease in plasma calcium and ultrafiltrable calcium after 1–21 hours of life. The minimum value was reached at 24–48 hours of life. An increase was then seen during the first week of life. Later in childhood total calcium and Ca_uf decreased continuously and significantly with age, and with the most marked rate during the first two-three years. The ultrafiltrable calcium fraction was found to be responsible for the changes in total plasma calcium. In 24–48 hours of life and 5–7 days of life protein-bound calcium was significantly lower as well. There were no significant differences between males and females in childhood.