Albumin excretion and renal haemodynamic response to physical exercise in normal and diabetic man

The relationship between exercise albuminuria and changes in renal haemodynamics during exercise in diabetes was investigated. In thirteen male, juvenile diabetic patients and seven comparable normal subjects GFR (125 I-iothalamate clearance) and RPF (131 I-hippuran clearance) as well as urinary albumin excretion were measured during the exercise test (450 kpm/min followed by 600 kpm/ min each for 20 min). All examined persons had normal baseline albumin excretion. The diabetics with a diabetes duration of 3-17 years exhibited increased albumin excretion during exercise, whereas there was no difference between the normals and the diabetics with less than 2 years of diabetes duration. The percentage changes during exercise in GFR, RPF and filtration fraction (FF) were at the same level in diabetics and normals. The FF was higher both in baseline values and during exercise for the two groups of diabetics when compared to the normals but no correlation between FF and albumin excretion could be demonstrated. Thus, elevated FF alone per se does not induce increase in albumin excretion. Systemic haemodynamics, heart rater and blood pressure, showed no difference between any of the groups. Concerning the abnormal albumin response in diabetics, it is concluded that the most likely explanation is that the glomerular membrane in these patients is unable to retain albumin when increased filtration pressure is operating during exercise. Altered renal haemodynamics during exercise may play a contributory role.