The effect of low-dose dopamine on renal haemodynamics in patients with type 1 (insulin-dependent) diabetes does not differ from normal individuals

It is well known that patients with Type 1 (insulin-dependent) diabetes exhibit both increased glomerular filtration rate and effective renal plasma flow, which can be found even when these patients are well controlled. Usually this is attributed to a decrease in renal vascular resistance and/or to enlarged kidney size and glomerular volume. Among the factors which govern glomerular filtration rate, renal plasma flow is most important. Renal plasma flow increases if renal vascular resistance decreases. The latter might exist in insulin-dependent diabetes mellitus because of either a predominantly afferent or a predominantly efferent vasodilatation. Dopamine is an agent which causes predominantly efferent vasodilatation. Therefore, the effects of infusing a low dose of dopamine on glomerular filtration rate and effective renal plasma flow in 12 well-controlled patients with Type I (insulin-dependent) diabetes and 28 healthy volunteers were compared to investigate whether the increased glomerular filtration rate in Type 1 diabetes is caused by an efferent vasodilatation. The median increase in glomerular filtration rate during dopamine infusion amounted to 13.0% in diabetic patients and 12.5% in healthy control subjects (n. s.). It is concluded that the elevated glomerular filtration rate in well-controlled Type 1 diabetes is not caused by a predominantly efferent vasodilatation.