Segmental tubular sodium reabsorption in type 1 diabetes

Segmental tubular sodium reabsorption in Type 1 (insulin-dependent) diabetes was measured in 36 patients in a cross-sectional study including one group (n = 13) without significant albuminuria (UalbV < 30 mg 24 h-1), one group (n = 16) with albuminuria in the range from 30 to 300 mg 24 h-1, and a group (n = 7) with nephropathy (UalbV > 300 mg 24 h-1). Lithium clearance was used to measure end proximal delivery. From end proximal delivery, 51Cr-EDTA clearance (GFR) and sodium clearance, segmental tubular reabsorption was calculated. For all patients, GFR was directly correlated with end proximal delivery (r = 0.62, p < 0.0005), while end proximal delivery was inversely correlated to fractional proximal reabsorption (r = -0.71, p < 0.0005). In the subgroup with UalbV less than 30 mg 24 h-1, the direct correlation between GFR and end proximal delivery was also significant (r = 0.77, p < 0.05). In the group with nephropathy (UalbV > 300 mg 24 h-1), mean GFR and end proximal delivery were decreased and fractional proximal reabsorption was increased, but there was still a positive correlation between GFR and end proximal delivery (r = 0.75, p < 0.05) and an inverse correlation between end proximal delivery and fractional proximal reabsorption (r = -0.85, p < 0.05). It is concluded that in these groups of diabetic patients the end proximal delivery is increased while GFR is increased.(ABSTRACT TRUNCATED AT 250 WORDS)