Abnormal albumin excretion after two provocative renal tests in diabetes: Physical exercise and lysine injection

Proteinuria, the first clinical sign of nephropathy, is generally not found during the first 10 to 15 years of diabetes mellitus. Using a sensitive radioimmunoassay for albumin, we also found normal excretion values in almost all patients in generally good diabetes control for the first many years of the disease [1–3]. Morphological changes in the kidney occur, however, very early in diabetes [4], and recently we showed that examinations during physical exercise disclose abnormalities in albumin excretion in patients with normal baseline values [5]. The evolution of changes and the involved mechanisms were, however, not established. Analysis of the final urine does not permit determination of the glomerular passage rate of albumin or any other protein, because unknown amounts of plasma proteins are reabsorbed by the proximal tubular cells. The discovery that arginine, lysine, and certain other amino acids inhibit tubular protein reabsorption opened, however, new possibilities in this field [6–8]. The aim of the present study was two-fold; namely, to examine more closely the development and mechanism of the abnormalities in albumin excretion emerging during exercise in diabetes and to evaluate a new kind of provocation test for protein excretion in similar groups of patients-that is, inhibition of tubular protein reabsorption by the use of lysine, the most strongly inhibiting substance examined so far [7].