Plasma catecholamines in acute magnesium deficiency in weanling rats

A controlled study was conducted to quantitate plasma catecholamines in magnesium-deficient weanling rats experiencing the seizure-shock episode. Eighty-four male Sprague-Dawley rats each weighing 35.6 +/- 0.3 g (mean +/- SEM) were fed purified diets to which was added 150 mg magnesium/100 g (Mg-150) or no magnesium (Mg-0). Studies were conducted between d 5 and 8. Plasma and bone magnesium and calcium were measured by atomic absorption spectrophotometry, and plasma catecholamines by radioenzymatic assay using 3H. Compared with Mg-150 rats, the Mg-0 rats showed reduced weight gain (P less than 0.001); reduced plasma magnesium (P less than 0.001) and reduced bone magnesium (P less than 0.001) with no corresponding changes in calcium concentration; and a 25% mortality by d 8. Pair-feeding and 80-dB noise provoked no changes in plasma catecholamines in Mg-150 rats, but both strychnine-induced seizures in Mg-150 rats and seizures induced by 80-dB noise in Mg-0 rats were accompanied by massive increases in plasma catecholamines. In contrast, 80-dB noise in Mg-0 provoked a massive increase in plasma catecholamines (P less than 0.001). However, gross pulmonary pathology developed only in Mg-0-shocked rats, not Mg-150-shocked animals. The study provides no evidence for a role of catecholamines in the pathogenesis of Mg-0 shock. The weanling rat displayed the ability to release massive quantities of three catecholamines during the final stages of acute magnesium deficiency and to normalize the plasma catecholamine levels within 16 h after seizure shock.