Changes in plasma, erythrocyte, and platelet magnesium levels in normotensive and hypertensive obese subjects during oral glucose tolerance test

We evaluated the 75-g oral glucose tolerance test (OGTT)-induced modificati ons in glucose, insulin, and norepinephrine plasma concentrations, and in p lasma, erythrocyte, and platelet magnesium levels in two groups of obese su bjects (normotensive obese, NT-Ob, N = 19; hypertensive obese, HT-Ob, N = 1 5), and in a group of healthy control subjects (N = 12), During OGTT we det ected a reduction in plasma magnesium concentrations and an increase in ery throcyte and platelet magnesium levels in the controls, whereas in both nor motensive and hypertensive obese subjects, there was a reduction in plasma, erythrocyte, and platelet magnesium levels. Furthermore, no statistically significant difference was detected among the groups studied as regards Del ta-plasma magnesium. On the other hand, Delta-erythrocyte magnesium and Del ta-platelet magnesium were negative in the NT-Ob (Delta-erythrocyte magnesi um: -0.24 +/- 0.08 mmol/L; Delta-platelet magnesium: -0.49 +/- 0.09 mu mol/ 10(8) cells) and HT-Ob (h-erythrocyte magnesium: -0.20 +/- 0.10 mmol/L; Del ta-platelet magnesium: -0.50 +/- 0.11 mu mol/10(8) cells) groups, and posit ive in control subjects (Delta-erythrocyte magnesium: 0.40 +/- 0.08 mu mol/ L; Delta-platelet magnesium: 0.47 +/- 0.09 mmol/ 10(8) cells). Finally, a d irect correlation was found between Delta-norepinephrine and Delta-erythroc yte magnesium (r = 0.80, P <.01) in the control group, and a negative corre lation was detected between Delta-norepinephrine and Delta-platelet magnesi um (r = -0.58, P <.05) in the HT-Ob group. Our results seem to indicate tha t the insulin resistance status, the hyperglycemia, and the disregulation o f the adrenergic system in obese subjects could be involved in the pathogen esis of the magnesium homeostasis impairment observed in the obese subjects . Am J Hypertens 1999;12:128-136 (C) 1999 American Journal of Hypertension, Ltd.