The glucose tolerance test is an important diagnostic procedure in metabolic diseases. As the test is currently employed, glucose is administered either orally or intravenously and there is no uniform interpretation of the results.A study of the rapid glucose tolerance test is found in a review by Tunbridge and Allibone (1). The present study was undertaken to test the validity of the concept that the rapid intravenous glucose tolerance test might properly and readily be interpreted by following the rate of disappearance of glucose from the blood. It was our hope also to evolve a simple test for routine use. The uniformity of the single injection method was studied as a means of separating the normal from the known mild diabetic patient. MATERIAL AND METHODSTwenty-five grams of glucose as a 30 per cent solution in distilled water were administered intravenously within four minutes. A fasting blood specimen was obtained, and then at four minutes following the glucose administration and subsequently every eight minutes for 72 minutes. Blood was obtained from an ear lobe that was kept moist with a heparin sponge. Determination of blood glucose was done by the Horvath and Knehr modification (2) of the Folin-Malmros micromethod (3).The control group consisted of 70 healthy men ranging in age from 25 to 50 years with no family history of diabetes mellitus. The test was repeated with 25 grams of glucose at intervals of from one to three months in 20 subjects, and with 35 grams of glucose in 13 who had been on an adequate carbohydrate intake. The abnormal group consisted of 26 patients with known mild diabetes mellitus controlled by diet alone (the majority had

The effect of the parenteral administration of magnesium sulfate on the renal hemodynamics of normal dogs (1) and normal children (2) has been previously reported. However, no data are available concerning the effects of magnesium sulfate on the excretion of other electrolytes, nor have studies on the renal clearance of magnesium been reported. It is the purpose of this report to present such data. METHODSStudies of renal function, electrolyte excretion, and the clearance of magnesium were performed on six young men without evidence of cardiovascular or renal disease. The experimental subjects received a normal hospital diet which contained between 7 and 15 grams of sodium chloride daily. The experiments were performed in the basal state after adequate hydration by the oral ingestion of one liter of water 60 to 90 minutes before the study. Renal plasma flow was determined by the clearance of para-aminohippurate according to the method of Goldring and Chasis (3) and utilizing a constant injection syringe as previously described (4) indicated that concentrations of magnesium exceeding those found in the urine in these experiments had no effect on the flame photometric determination of sodium or potassium. Chloride was determined by the method of Schales and Schales (6). Serum magnesium was determined by the molybdivanadate method of Simonsen, Westover, and Wertnan (7). Urinary magnesium was determined by a similar method as modified by Stutzman (8). RESULTSThe control values for renal hemodynamic, electrolyte excretion, and magnesium clearance studies are the averages of three consecutive periods. The values during the constant intravenous administration of magnesium sulfate are the averages of three consecutive periods beginning 45 minutes after the start of the infusion.There was a significant decrease in mean renal plasma flow (t = 3.45, p 0.02-0.01) and in glomerular filtration rate (t = 5.98, p < 0.01). Although the mean percentage change was slight, being 9.9 per cent for renal plasma flow and 8 per cent for glomerular filtration rate, both functions decreased in each patient. Since the statistical analysis was done by the method of paired controls (t = t24 and since the changes were all in the n/ same direction, these changes in renal plasma flow and glomerular filtration rate are statistically significant. However, the degree of change does not imply physiologic significance. The filtration fraction increased in three patients and decreased in three. The clearance data are recorded in Table I.The serum sodium, potassium, and chloride concentrations were unchanged by the administration of magnesium sulfate. An increase in the urinary sodium and chloride excretion and a decrease in potassium excretion occurred in each patient and 858

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