Magnesium metabolism during total parenteral nutrition in rabbits

Magnesium metabolism was studied during total parenteral nutrition (TPN) in rabbit. Rabbits were fed for 14 to 17 days by TPN of 110 Cal/kg/day with different doses of magnesium. Results were as follws: 1. Excretion of magnesium during starvation was 1.5 mEq/kg/day. The urinary Mg/N excretion ratio was 3.4 mEq/Ng. 2. An intake of 2.5 mEq/kg/day of magnesium was required to maintain normal plasma and erythrocyte magnesium levels, plasma P and Ca should be supplied at the rate of 9 mEq/kg/day (8.2 mEq/100Cal) and 1 mEq/kg/day respectively. 3. The excretion of magnesium, phosphorus and potassium increased during low calorie parenteral nutrition. 4. Although no depletion of nitrogen balance and body weight occurred during TPN with-out magnesium, impairment of K, P and Ca utilization was suspected. 5. This study of magnesium balance showed that magnesium may be required at early stages of TPN. 6. Magnesium deficiency was diagnosed by a fall in the levels of plasma magnesium, erythrocyte magnesium, and urinary magnesium excretion. This experiment indicates that TPN which includes quantities of magnesium may be needed for the metabolism of K, P and Ca.