Intralymphocyte free magnesium and calcium and insulin tolerance test in a group of essential hypertensive patients

Abstract

In order to assess the links which are claimed to exist between peripheral insulin resistance and intracellular magnesium and calcium concentrations, we measured free intralymphocyte magnesium (Mg i) and calcium (Ca i) concentrations as well as the rate constant of plasma glucose disappearance (K itt) after insulin injection (insulin tolerance test: ITT) in a group of 16 normotensive control subjects (NC) and 34 essential hypertensive subjects (EH). Mg i and Ca i were measured in triplicate by means of a fluorimetric technique based on the dyes furaptra and fura-2 respectively. K itt values proved significantly reduced in EH as compared to NC (M ± SD, EH: 4.49 ± 1.31 vs 5.28 ± 1.19, P < 0.05; 95% confidence limits: 0.23–1.5). Mg i and Ca i were not statistically different in EH as compared to NC subjects (Mg i, NC: 266 ± 20 μmol l ; EH: 245 ± 50 μmol l ; Ca i, NC: 47 ± 9 nmol l , EH: 46 ± 13 nmol l ). We found a statistically significant inverse correlation in the whole study group between K itt and body mass index (R = −0.363, P < 0.01) and a statistically significant positive correlation between K itt and Mg i (R = 0.347, P = 0.013) was found. In a step-up multivariate regression analysis including blood pressure, plasma lipids, BMI, plasma magnesium, fasting insulin, fasting glucose, Mg i and Ca i, the dependent variable K itt is statistically significantly correlated with body mass index and Mg i. In a first attempt to study the relationships between insulin resistance, Mg i and Ca i in nucleated cells, the chosen index of peripheral resistance seems to be linked to intracellular free magnesium.