[Pathophysiologic mechanisms of early changes in renal hemodynamics in diabetes mellitus]

The early stages of diabetes mellitus are in some patients associated with renal haemodynamic changes resulting in increased glomerular filtration. This "diabetic hyperfiltration" is considered to be one of pathophysiological mechanisms and risk factors for the development of diabetic nephropathy. The aim of this paper is to review some contemporary views on pathophysiological mechanisms leading to this disorder with emphasis on the role impaired activity of humoral factors influencing renal haemodynamics. In addition to poor metabolic control due to insulinopenia there is a convincing experimental evidence suggesting the role of atrial natriuretic factor and endothelium-derived nitric oxide in mediating renal haemodynamic changes in diabetes. Enhanced renal activity of angiotensin I converting enzyme resulting in local overproduction of angiotensin II and accelerated degradation of kinins may be another factor contributing to the genesis of diabetic hyperfiltration. Hyperglycaemia induces changes in cellular signalling of these vasoactive systems. Furthermore, diabetes is a state of decreased capability of renal vascular bed to autoregulate blood flow likely due to altered activity of tubuloglomerular feedback and ion channels.