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.