Arterial hypertension--a disease of the juxtaglomerular apparatus?

From a special strain of genetically hypertensive rats, the Milan hypertensive strain (MHS), arterial hypertension can be transplanted with the kidney to the Milan normotensive strain (MNS). During development of hypertension in MHS rats there was an activation of the tubuloglomerular feedback control that reduced glomerular filtration rate, leading to retention of electrolytes and fluid. This increased extracellular fluid volume reduces feedback sensitivity, but in a fashion that gives rise to chronic extracellular fluid expansion and can thereby raise the blood pressure. In a limited sense, arterial hypertension in these animals exists to prevent the kidney from retaining more extracellular fluid volume. The altered function in the juxtaglomerular apparatus of the MHS rats thus may explain the rise in arterial blood pressure.