SHIMAMOTO, K., HIGASHIURA, K., NAKAGAWA, M., MASUDA, A., SHIIKI, M., MIYAZAKI, Y., ISE, T., FUKUOKA, M., HIRATA, A. and IIMURA, O. Effects ofHyperinsulinemia under the Euglycemic Condition on Calcium and PhosphateMetabolism in Non-Obese Normotensive Subjects. Tohoku J. Exp. Med., 1995, 177 (4), 271-278 - The effect of acute insulin infusion on the metabolism of calcium (Ca) and phosphate (P) was examined in 17 healthy subjects. They were hospitalized and kept on a constant diet for 5 days, and an euglycemic hyperinsulinemic glucose clamp was applied. Synthetic human insulin was infused at the rate of 40 mU/m2/min for 2hr, and glucose was also infused to maintain basal glucose levels of each subject. The control study was performed in 8 of the 17 subjects, into whom 10% xylitol was infused for 2hr at the rate of 100ml/hr. The plasma insulin concentrations were 7.94±0.35 and 62.3±143mU/liter before and after the glucose clamp technique, but serum free Ca ion was increased significantly (p< 0.05), and serum P and serum parathyroid hormone (PTH) were decreased significantly (ppp<0.05) under the hyperinsulinemic condition. The results suggested that, under the conditions of euglycemic hyperinsulinemia by glucose clamp technique, insulin increased the serum free Ca ion, and as a result, PTH was suppressed. Decreased PTH might induce calciuresis and enhance tubular P reabsorption under hyperinsulinemia. Insulin increased serum free Ca ion might relate to the vasodilating action of insulin by its decrease of intracellular free Ca ion in vascular smooth muscle. - hyperinsulinemia; glucose clamp technique; Ca metabolism; P metabolism; PTH