Calcium Mobilization Studies with Young Dairy Calves

Abstract

Summary Young dairy bull calves were injected intravenously with solutions of the disodium salt of ethylenediaminetetraacetic acid (Na 2 EDTA) at various rates and amounts. The effect of the injections was ascertained by analyses of the oxalate-precipitable blood serum calcium and plasma inorganic phosphorus before, during, and after injection. The rate of administration of Na 2 EDTA in the single injection phases of the study varied from 17.7 to 5.1 mg/kg/min. The level to which the serum calcium is lowered is a function of the rate and amount of chelating agent injected. Oxalate-precipitable blood serum calcium reduced to tetanic levels is restored to preinjection levels within 2 hr. postinjection. The response of plasma inorganic phosphorus was variable. There was considerable variation among calves in the levels of oxalate-precipitable calcium at which tetany occurred. It is postulated that the rapidity with which the blood serum calcium levels was replenished indicates that calves have a large labile source of calcium. A chelating agent, the disodium salt of ethylenediaminetetraacetic acid (Na 2 EDTA), when injected intravenously combines with the blood serum calcium. The sodium ion of the chelate is displaced by calcium which forms a soluble, non-ionizable, physiologically unavailable complex with EDTA that is not precipitated with oxalate. EDTA thus provides a tool for immediate lowering of the blood serum calcium, so that the rate of mobilization of calcium may be studied.