DIURNAL-VARIATION IN GLOMERULAR CHARGE SELECTIVITY, URINARY ALBUMIN EXCRETION AND BLOOD-PRESSURE IN INSULIN-DEPENDENT DIABETIC-PATIENTS

The urinary albumin excretion rate (AER) in a subgroup of patients wit h insulin-dependent diabetes mellitus (IDDM) steadily increases. In th ese patients a concomitant reduction of the glomerular charge selectiv ity index (SI) has been demonstrated. The aim of the present study was to evaluate whether diurnal variation in AER could be related to a di urnal variation in SI and/or a diurnal blood pressure variation. Thirt y-three patients with IDDM, 27 with normal albumin excretion (AER <20 mu g/min; group D-0) and six with incipient nephropathy (AER from 20 t o 200 mu g/min; group D-A), were studied. AER and SI (renal clearance ratio of total-lgG/IgG(4)) were measured in three different urine coll ecting periods: period A (8:00 a.m. to 12:00 a.m.), period B (12:00 a. m. to bedtime) and period C (bedtime to 8:00 a.m.), A significant incr ease in SI was seen during the nighttime: period A, 1.6 (0.2 to 3.8; m ean, range); period B, 1.7 (0.3 to 3.0); and period C, 2.0 (0.2 to 4.0 ); P = 0.01. Corresponding to this observation, an overall significant decrease in AER was found: period A, 10 (3 to 137) mu g/min (median, range); period B, 8 (3 to 84) mu g/min; and period C, 5 (0 to 78) mu g /min; P < 0.001. In all three sampling periods a negative correlation was found between AER and SI. When group D-0 was analyzed alone, the r esults were similar. Diurnal variation in blood pressure was significa ntly positively correlated with AER in group D-A, but was not correlat ed to variation in AER in D-0. We suggest that in normoalbuminuric IDD M patients diurnal variation in AER is related to diurnal variation in SI.