1. Exercise-induced changes in renal haemodynamics, water homoeostasis, urinary albumin excretion and their possible relation to plasma noradrenaline were studied in seven insulin-dependent diabetic children and adolescents without signs of autonomic or somatic neuropathy. Six age-matched clinically healthy patients in remission from the minimal change nephrotic syndrome served as controls.
2. The diabetic patients had a higher glomerular filtration rate and effective renal plasma flow and a lower venous plasma noradrenaline level in the basal state. They also had a higher systolic blood pressure compared with the controls. During exercise the diabetic patients showed a less marked reduction in glomerular filtration rate and urinary flow and a greater increase in filtration fraction. Their heart rate increase during exercise was lower. An inverse correlation between the percentage changes in noradrenaline and glomerular filtration rate during exercise was noted solely in the diabetic patients. They also showed a less marked increase in the ratio between potassium and sodium clearances during and 20 min after exercise. Albumin excretion did not differ between the two groups.
3. We suggest that the sympatho-adrenergic effects of exercise on heart rate, renal haemodynamics and water homoeostasis are blunted in our diabetic patients. Hence, signs of impaired sympathetic activity might be disclosed in young diabetic patients with a disease of fairly short duration.