Role of the kidney in the genesis of hypertension: aberrant renal response to excess salt intake.

1. The kidney maintains the milieu intérieur of the body. To effectively achieve this function, the kidney must maintain a high glomerular filtration rate and high reabsorption in the face of limited salt intake or low extracellular volume and in the face of changes in systemic blood pressure. 2. Autoregulation of the renal blood flow and glomerular filtration rate is therefore critical. In addition to myogenic responses as seen in the resistant artery of other organs, the juxtaglomerular apparatus (JGA) plays a critical role in the autoregulation of the renal plasma flow and glomerular filtration rate through tubuloglomerular feedback (TGF). 3. The fact that the JGA and TGF appear first in amphibian species in evolution suggests that the transition from aquatic life to terrestrial life required this particular structure and function of the kidney. 4. Salt intake in natural environments is often very limited and chronic excess salt intake is a habit peculiar to humans in recent culture. Thus, it is hypothesized that TGF is primarily set to maintain high GFR in the face of low salt intake. 5. Resetting of TGF to salt-loading may exist in hypertension animal models which retards salt excretion. Renal cross-transplantation studies also indicate the principal role of the kidney as the primary organ responsible for the genesis of hypertension. 6. It is suggested that abnormalities as abnormal response of TGF in response to salt-loading may underlie the genesis of essential hypertension in humans. Indeed, hypertension is not seen in human cultures with very low salt intake.