Diuretic agents and glucose reabsorption

Renal glycosuria in renal homograft recipients

Transient renal glycosuria was observed in eight renal transplant patients during the recovery phase from initial tubular necrosis or acute rejection. In these subjects and three homograft recipients without glycosuria we performed glucose titration experiments. Three patients were found to have type A glycosuria, two had type B and three type C. The titration curve was normal in the three patients without glycosuria. In addition, most subjects presented with hypophosphataemia and hyperphosphaturia. Apart from a direct correlation between the point of splay of the glucose titration curves and the fractional clearance of phosphate, there was no clear-cut relationship between the handling of glucose and phosphorus. Mild hyperchloraemic acidosis was observed in six subjects, but this was unrelated to the type and grade of glycosuria. It is concluded that in homograft recipients the tubular alterations have a patchy and unpredictable distribution and may cause a variety of symptoms which do not necessarily occur in close association.

Renal glycosuria in patients with the nephrotic syndrome

Transient or persistent renal glycosuria may occur in patients with the nephrotic syndrome. In an attempt to elucidate its mechanism, glucose titration experiments were performed in 20 nephrotic patients. The type A titration curve was found in one and type B in four patients with severe organic changes and low glomerular filtration rate. The remaining subjects displayed a particular type of curve (type C) characterized by a low point of splay but an otherwise almost physiological tracing. In type B and C patients the maximal rate of reabsorption per ml glomerular filtrate (TmG/GFR) was significantly increased and correlated inversely with the filtration fraction. In these patients the point of splay correlated with the glomerular filtration rate and the sodium clearance, but not with the plasma albumin concentration or the rate of proteinuria. These observations suggest that type A was due to diffuse tubular atrophy, and type B to increased nephron heterogeneity resulting from chronic organic changes. Type C was presumably caused by a potentially reversible alteration of the late proximal or distal glucose transport related to the nephrotic syndrome itself.