Genetic hypertension and the kidney

Alterations in sodium metabolism as an etiological model for hypertension

An adequate matching for race, sex, stage of the menstrual cycle, family history of hypertension, and the amount of sodium and other electrolytes in the diet should be a prerequisite for valid conclusions when interpreting the erythrocyte concentration and fluxes of sodium in essential hypertensive patients in comparison with normal subjects. Alterations in intracellular sodium concentration and transmembrane sodium transport systems as causes of essential hypertension are postulated. This review article describes how this abnormal sodium and calcium metabolism translates into increased systemic vascular resistance through altered vasoactive responses and/or vasculature structural changes.

Pathogenesis of the essential hypertensions

The pathogenesis of essential hypertension (EH) is reviewed with a special focus on the development phase or the pre-hypertensive period. Three animal models are presented: the spontaneously hypertensive rat, the Dahl's salt-sensitive rat, and the Milan hypertensive rat. Some of the findings in animal models have inspired new fields and technical approaches for studying EH in man. From the original idea of Page, a new mosaic of various etiological parameters serves as a basis for reviewing the multiple facets of EH in man. One must conclude that EH is heterogeneous disease and most likely every single hypertensive patient belongs to a subgroup of the whole population of hypertensives.

Presence of a potential-sensitive Na+ transport across renal brush-border membrane vesicles from rats of the Milan hypertensive strain

Sodium transport was measured in brush-border membrane vesicles prepared from kidney cortex of the Milan hypertensive strain (MHS) rats and the corresponding normotensive controls. In the presence of an outwardly directed proton gradient, 22Na was transiently accumulated in the vesicles. When a transmembrane electrical potential was imposed across membrane vesicles, both the accumulation ratio and the initial uptake were increased, indicating the presence of an electrogenic pathway for sodium in these membranes. The potential-dependent sodium uptake was significantly higher in MHS rats. Kinetic analysis give simple Michaelis Menten curves in the presence and in the absence of a membrane potential. In both conditions Jmax was significantly increased in MHS rats, whereas Km was the same for the two rat strains. Sodium uptake was inhibited by amiloride at concentrations that inhibit Na+-H+ exchange. The presence of the higher, potential-sensitive, sodium uptake in MHS is in agreement with studies on renal physiology which support the hypothesis that an increase in tubular sodium reabsorption may be the primary cause for the development of hypertension in this rat strain.