MG-28

Mg28 of a high specific activity was used in these studies. It was rapidly injected intravenously into 12 dogs and the concentration-time course curves in plasma were obtained. Urinary and fecal excretion was followed in seven animals. The dogs were killed 7 min to 68 hr following injection. Seventy-four tissues were sampled and assayed for Mg28 concentration. Plasma Mg24 was determined by flame spectrophotometry. With these data it was possible to follow the concentration-time course of Mg28 in the various tissues as well as to calculate their "exchanging" Mg24 content and effective rates of exchange. A variation in the pattern of uptake and in concentration of exchanging Mg24 was noted among the different tissues. During the interval from 24–68 hr, body exchanging Mg24 space and mass were found to range from 3.2–3.8 liters/kg and 4.9–5.7 mEq/kg, respectively. The biologic half-life of Mg28 in the dog estimated from excretion data was 11 days.

Intravenous injections of Mg²⁸ were given to 7 normal controls, 5 cirrhotics, and 4 alcoholics.Serum and urine exchangeable Mg was determined 24 hrs. later.Four of the 5 cirrhotics had serum exchangeable Mg values below those of control subjects of the same height.The 4 patients with recent acute alcoholism showed even lower values.Owing to the small number of tests, there was some scattering of values.In the alcoholic patients the serum Mg was lower than in the other 2 groups, while the urinary Mg was markedly diminished.The low Mg excretion probably resulted from poor food intake, hypomagnesemia, and depletion of body Mg.The loss of Mg may occur both through the urine and the feces.In edematous cirrhotics increased aldosterone levels may be a factor in producing Mg deficiency.Recent studies have shown that an intake of EtOH causes an acute Mg diuresis which is independent of water diuresis. 25 references.