Renal Glomerular and Tubular Function following Acute Insulin Deprivation in Juvenile Diabetes mellitus

Abstract

The effects of acute deprivation of insulin on renal glomerular and tubular functions were studied in 10 children with juvenile diabetes mellitus. Serum glucose concentrations were similar when insulin was administered (251 ± 112 mg/dl) and when it was withheld (306 ± 130 mg/dl; 0.5 > p > 0.2). Acute insulin deprivation was associated with a significant reduction in glomerular filtration rate, from 151 ± 48 ml/min/1.73 m² to 114 ± 41 ml/min/1.73 m² (p < 0.01). The fractional excretion of sodium rose from 0.45 ± 0.43 to 0.85 ± 0.54% (p < 0.05) and was associated with an enhanced natriuresis; the urinary excretion of sodium increased from 1.67 ± 1.23 to 2.43 ± 1.72 µEq/min/kg body weight (p < 0.05), whereas the urinary excretion of phosphate was not significantly altered from control values. During insulin deprivation a drop occurred in the serum concentration of calcium from 10.37 ± 0.52 to 9.73 ± 0.61 mg/dl (p < 0.01) as well as in its urinary excretion from 0.34 ± 0.24 to 0.24 ± 0.20 µg/min/kg body weight (p < 0.01). The serum concentration of potassium rose from 4.44 ± 0.41 to 4.96 ± 0.51 mEq/1, but its urinary excretion was not significantly different from control values. These data suggest that in juvenile diabetes mellitus the acute deprivation of insulin, dissociated from fluctuations in serum glucose concentration, is associated with a fall in glomerular filtration rate, an increased natriuresis, and a modified calcium and potassium homeostasis.