Decreased urinary excretion of dopamine and sodium in diabetic children with incipient nephropathy.

It has been suggested previously that a decrease in urinary dopamine output might be related to a decrease in the urinary sodium excretion in subjects with diabetic nephropathy suffering from type 2 diabetes. To investigate the renal dopamine status in children with type 1 (insulin-dependent) diabetes mellitus, we measured the 24-hour urinary excretion of dopamine, norepinephrine and sodium in 12 patients with incipient nephropathy (group A, 24-hour albumin excretion rate 70-200 micrograms/min), in 20 age matched patients with normal microalbuminuria (group B, AER less than 20 micrograms/min) and in 8 healthy controls (group C). The mean values for urinary excretion of dopamine and norepinephrine were significantly lower in group A compared to groups B and C (25.6 +/- 14.8 vs. 65.9 +/- 25.5 and 73.3 +/- 18.0 micrograms/day, p less than 0.001 and 11.8 +/- 4.6 vs. 25.1 +/- 12.1 and 28.4 +/- 8.9 micrograms/day, p less than 0.01, respectively). The mean value for the urinary excretion of sodium was also significantly lower in group A than in groups B and C (98.4 +/- 24.1 vs. 206.2 +/- 59.5 and 198.1 +/- 42.8 mEq/day, p less than 0.01). The 24-hour urinary excretion of dopamine correlated significantly with the sodium excretion (r = 0.65, p less than 0.001). Arterial blood pressure was elevated in group A compared to group C (p less than 0.01). Our results suggest that a decrease in endogenous dopamine could play a role in the low urinary sodium excretion thereby resulting in sodium retention which may in turn lead to the development of higher blood pressure in diabetic children with incipient nephropathy.