Submaximal exercise provokes an abnormal elevation in albuminuria in type 1 (insulin-dependent) diabetes mellitus. Plasma catecholamines might be involved in this phenomenon by a renal vasoconstrictive effect. Twelve healthy subjects (Controls: albuminuria < 10 micrograms min-1), 13 normoalbuminuric type 1 diabetic patients (DNormo: albuminuria < 10 micrograms min-1) and 13 microalbuminuric type 1 diabetic patients (DMicro: albuminuria 10-200 micrograms min-1) performed a fixed bicycle workload (600 kpm for 20 min+urine collection 40 min post exercise). None of the patients suffered from autonomic neuropathy or hypertension. Fractional albumin clearance (FalbCl) rose in DNormo (p = 0.02) and DMicro (p = 0.01) but not in the Controls (p = 0.40). Basal plasma adrenaline and noradrenaline were not different in the three groups. The increments in noradrenaline were more pronounced in DNormo and DMicro than in Control (Controls < DNormo, p < 0.05; Controls < DMicro, p < 0.01). The changes in FalbCl were significantly correlated with the changes in noradrenaline (all subjects r = 0.65, p < 0.001). The increments in adrenaline were not different in the diabetic groups compared to the controls, and were not related to the changes in FalbCl. Multiple regression analysis showed that changes in plasma noradrenaline (p < 0.002) and in mean arterial pressure (p < 0.005) independently contributed to the changes in FalbCl (multiple r = 0.73). It is concluded that the exercise-induced plasma noradrenaline response is increased in normo- and microalbuminuric type-1 diabetic patients. Noradrenaline appears to contribute in the exercise-induced changes in renal protein handling, possibly by its effect on renal haemodynamics.
