Adaptations of the renal microcirculation to hypertension

Control of glomerular filtration involves sensitive regulation of glomerular filtration pressure over a widely varying range of systemic arterial pressures. This control is exerted through precise adjustments in preglomerular resistance involving numerous activation and feedback mechanisms. Under physiological conditions, these mechanisms succeed in maintaining renal blood flow and glomerular filtration rate in normal ranges and they provide protection of the glomerulus from elevated arterial pressure. However, under pathophysiological conditions, the accuracy of that regulation can be compromised. In hypertension, the efficiency with which preglomerular resistance is controlled is impaired. This can result in greater transmission of arterial pressure to glomerular capillaries, leading to inappropriately high glomerular filtration pressures and glomerular damage. Chronic exposure to hypertensive conditions can also lead to modification of the structure and/or function of the renal microvasculature as an adaptive response to the hypertension. Distinguishing adaptive, and thus protective, alterations in renal microvascular function from those that reflect deterioration of microvascular function is an important challenge. Inappropriate modifications in renal microvascular performance can lead to deterioration of glomerular function and can ultimately result in end-stage renal disease. This review will take a detailed look at the alterations in autoregulatory, vasoconstrictor, and vasodilatory responsiveness of the renal microcirculation during hypertension. It is anticipated that a more thorough understanding of the renal microcirculatory adaptations to hypertension will lead to better therapeutic approaches to managing hypertension while at the same time providing better protection to long term kidney function.