Proximal glomerulo-tubular balance in patients with type 1 (insulin-dependent) diabetes mellitus.
To evaluate the glomerulo-tubular balance of sodium and water in the proximal tubules of diabetic patients with elevated glomerular filtration rate, the renal plasma clearance of lithium and the glomerular filtration rate (51Cr-EDTA plasma clearance) were determined simultaneously in 11 ambulatory Type 1 (insulin-dependent) diabetic patients (aged 25-35 years) with no evidence of diabetic nephropathy and in 10 age-matched healthy subjects. The renal plasma clearance of lithium, which is a measure of flow from the proximal tubule into the thin descending limb of the loop of Henle, did not differ between diabetic and control subjects (28.9 +/- 4.0 versus 28.3 +/- 5.1 ml/min per 1.73 m2 surface area, mean +/- SD), whereas the glomerular filtration rate in the diabetic patients was significantly higher than in the control subjects (136 +/- 10.2 versus 108 +/- 13.6 ml/min per 1.73 m2, p less than 0.001). The same held true for the fractional reabsorption rate in the proximal tubules (78.7 +/- 3.2 versus 73.6 +/- 4.9%, p less than 0.02). The results indicate that the elevation of the glomerular filtration rate in diabetic patients is associated with a parallel increase in the proximal reabsorption rate. This type of glomerulo-tubular balance implies that the flow of water and flux of sodium to the segments distal to the proximal tubule are kept constant during variations in the glomerular filtration rate.
D000042:Absorption; D000328:Adult; D003922:Diabetes Mellitus, Type 1 / Q000378:metabolism*; D005260:Female; D005919:Glomerular Filtration Rate; D005947:Glucose / Q000378:metabolism; D006801:Humans; D007678:Kidney Glomerulus / Q000378:metabolism*; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D008297:Male; D010710:Phosphates / Q000378:metabolism; D012964:Sodium / Q000378:metabolism
D010710:Phosphates; D012964:Sodium; D005947:Glucose