The distribution of exchangeable magnesium within the sheep

Abstract

that after the intravenous administration of 28Mg the decline in the specific activity of the plasma or urinary magnesium can be expressed as the sum of several exponential terms. Two general methods have been proposed for the solution of such a multi-termed equation for the entire system. The choice between these methods is important, since substitution of a single-term exponential equation for a multi-term one will provide erroneously high values for the size of the total exchangeable pool and of the unidirectional exchange rates. This will be demonstrated below.In the first method Care (1960) described the fall in plasma specific activity of magnesium, S(t), with time by the general equation S(t) = Ale klt + A2e-k2t + A3e-kt.He assumed that each term describes the behaviour of magnesium in a different pool and defined the size of each pool Q1, Q2 and Q3 as: injected per unit weight of magnesium. A system was postulated in which the 28Mg moved from one pool to the next successively, homogenization in each pool preceding each step.In the second method, used by Aubert & Milhaud (1960) to describe the time course of the plasma specific activity of calcium in man, the blood was represented as the central pool, the calcium of which exchanges simultaneously with that of three other pools in parallel with it; that is, a mammillary system was postulated with the blood as the central * Present address: The Rowett Research Institute, Bucksburn, Aberdeen.

Magnesium physiology and clinical therapy in veterinary critical care

“…Although all cells contain magnesium, the largest tissue fraction is in bone (67%) . Most bone magnesium lies within the mineral lattice with a lesser amount part of the surface‐limited exchangeable pool . Skeletal muscle contains 20% and other soft tissues contain 19% of the total body magnesium.…”