Urinary magnesium loss in aging diabetic mellitus rats

Past studies on urinary loss of magnesium (Mg) have focused on young diabetic rats. The aims of the present study were to determine the rapidity at which glycosuria and magnesuria occur after the induction of diabetes mellitus (DM) in old male rats, and the maximal amount of Mg and glucose (Glu) loss in the urine and whether or not the loss is persistent and (3) the most sensitive means of correlating the Mg and Glu loss in the urine. Three methods of expressing urinary Mg and Glu concentrations were selected: Method A: mg/24 h; Method B: mg/24 h/kg body weight (BW), and Method C: ratio of Mg to creatinine (Mg/Crea) or ratio of Glu to Crea (Glu/Crea). Our study indicated a maximal and rapid loss of Mg and Glu occurring within 1 week after induction of DM (by streptozotocin injection) and remained in effect for 6 weeks, the end of the study. The urinary Mg loss due to DM correlated best with urinary Glu when expressed as mg/24 h/kg BW. In addition, the increase in urinary Mg concentration paralleled the degree of glycosuria and reached a maximum of 5-12 times baseline values when expressed by Method B. This was 4-10 times when expressed by Method A, and 2-6 times when expressed by Method C. Since polyuria is a feature of DM, we also correlated the relationship between these two factors, and found a significantly positive correlation (r = 0.735) particularly when Mg was expressed as mg/24 h. In summary, rapid and significant urinary Mg loss is observed in old rats made diabetic with streptozotocin.(ABSTRACT TRUNCATED AT 250 WORDS)