Renal tubular function and urinary acidification capacity in early juvenile diabetes

Renal elimination of uric acid, calcium, phosphorus, sodium, potassium, chloride and magnesium and urinary acidification capacity were determined in ten insulin-dependent diabetics and in ten matched control subjects. The diabetics showed excessive excretion of uric acid, sodium, potassium, chloride and ammonia. Sodium, chloride and ammonia excretion fractions was also increased with respect to controls. The enhanced excretion of these substances in diabetics failed to relate to glomerular filtration rate, glycosuria or insulin requirements. These findings might be explained on the basis of glomerular filtration rate elevation, tubular response to this increment, and the underlying metabolic disturbances of diabetes.

Relation of kidney size to kidney function in early insulin-dependent diabetes

Renal function and renal size have been studied in ten early insulin-dependent diabetic patients and in ten matched control subjects. Glomerular filtration rate, renal plasma flow and radiological kidney size were determined in each subject. Glomerular filtration rate and renal plasma flow were increased in diabetics (mean +/- SD: 169.6 +/- 16.1 and 690.1 +/- 52.6 ml/min/1.73 m2, respectively) compared with controls (120.6 +/- 9.7 and 605.9 +/- 67.2 ml/min/1.73 m2; p less than 0.001 and p less than 0.01). Calculated kidney weight corrected to 1.73 m2 of body surface area was elevated in diabetics (385.2 +/- 29.0 g) with respect to controls (277.5 +/- 17.5 g; p less than 0.001). No significant differences were found between diabetics and control subjects when glomerular filtration rate was expressed per gram calculated kidney weight, while renal plasma flow was significantly lower in diabetics than control subjects when so expressed (p less than 0.01). A positive correlation was found between glomerular filtration rate, renal plasma flow and kidney size in both controls and diabetics (p less than 0.01 in all cases). These findings support the conclusion that in the early state of diabetes glomerular hyperfunction is related to enlargement of the kidneys and augmented renal plasma flow.