Changes in the Blood Calcium Associated with Egg Shell Calcification in the Domestic Fowl

Abstract

THE non-diffusible calcium of the plasma is almost entirely protein-bound, and in laying hens, and cocks treated with oestrogen, it is the phosphor-protein fraction which is chiefly responsibe for the binding of the calcium (Riddle, 1942: Urist, Schjeide and McLean, 1958). The diffusible calcium, which appears to be in equilibrium with the non-diffusible, consists mainly of ionic calcium together with small amounts of complex calcium ions, of which the Ca citrate ion is the most important. The equilibrium between the diffusible and non-diffusible fractions is greatly influenced by changes in pH (Seekles, 1936; Hopkins, Howard and Eisenberg, 1952), a decrease in pH resulting in an increase in the diffusible calcium level, due to the displacement of Ca++ ions from the proteins by H+ ions, an increase in pH having the opposite effect. This phenomenon does not appear to have been studied in the plasma of the domestic fowl, and it …