Furosemide and dDAVP for the treatment of pseudohypoaldosteronism type II

The molecular basis of pediatric hypertension

Blood pressure, the product of cardiac output and peripheral vascular resistance, follows a circadian rhythm and is altered by a host of circulating and local substances and by many physiologic events. The number of genes, signaling pathways, and systems involved in blood pressure regulation is enormous, and dissecting those factors that are most important in hypertension has proven challenging. This article discusses molecular mechanisms of hypertension in several conditions in which mutations in a single gene give rise to hypertension and then considers the contribution of these and other genes to essential hypertension.

Hereditary disorders of potassium homeostasis

There has been a dramatic recent increase in the understanding of the renal epithelial transport systems with the identification, cloning and characterization of a large number of membrane transport proteins. The aim of this chapter is to integrate this body of knowledge with the understanding of the clinical disorders that accompany gain, loss or dysregulation of function of these transport systems. The specific focus is on the best-defined human clinical syndromes in which there are derangements in potassium (K(+)) homeostasis. The focus is on inherited syndromes, rather than on acquired syndromes due to tubular transport defects, and the therapeutic approaches address chronic derangements of K(+) homeostasis rather than acute interventions directed at life-threatening hyperkalaemia.

Renal genetic disorders related to K+ and Mg2+

The recent knowledge of the renal epithelial transport systems has exploded with the identification, cloning, and characterization of a large number of membrane transport proteins. The fundamental aspects of these transporters are beginning to emerge at the molecular level and are summarized in the accompanying contributions in this volume of the Annual Review of Physiology. The aim of my review is to integrate this body of knowledge with the understanding of the clinical disorders of human mineral homeostasis that accompany gain, loss, or dysregulation of function of these transport systems. The specific focus is on the best defined human clinical syndromes in which there are derangements in K(+) and Mg(2+) homeostasis.

Phenotypic and genetic heterogeneity of familial hyperkalaemic hypertension (Gordon syndrome)

1. Familial hyperkalaemic hypertension (FHH), also called pseudohypoaldosteronism type II (PHA2) or Gordon syndrome, is a rare Mendelian-form of low-renin hypertension. The first cases of FHH were reported approximately 30 years ago and they described the peculiar biochemical abnormalities (i.e. hyperkalaemia and hyperchloraemic acidosis despite a normal glomerular filtration rate). 2. Since then, more than 90 single cases and families have been reported in the literature. These various reports show marked differences in phenotype. 3. Our group has now collected 14 unrelated pedigrees originating from different parts of France and Europe. We confirm the large variations in the age of discovery and in the severity of the biochemical abnormalities from one individual to another and from one family to another one. 4. Blood pressure levels have no significant relationship with hyperkalaemia or hyperchloraemia, but there is a positive relationship with age, as in the normal population. 5. Analyses of clinical features and Mendelian segregation in our families demonstrate autosomal-dominant inheritance, as expected from the literature. 6. Efforts have been made in the past years to unravel the gene responsible for the disease. Until now, a primary responsibility of the gene encoding the thiazide-sensitive Na-Cl cotransporter (SLC12A3) has been excluded in PHA2 families. Three loci have been identified on chromosomes 1 (PHA2A), 17 (PHA2B) and 12 (PHA2C). 7. More recently, analysis of three additional pedigrees, including 10 affected subjects, with over 25 members allowed us to demonstrate further genetic heterogeneity and the existence of at least a fourth locus. 8. The genetic heterogeneity of this syndrome, and thus the variety of molecular defects, suggests the role of either several new components of the same pathway, multiple aldosterone- regulated effectors or direct or indirect partners of the Na-Cl cotransporter.

Genetic heterogeneity of familial hyperkalaemic hypertension

BACKGROUND

Familial hyperkalaemic hypertension (FHH) is a Mendelian form of low-renin hypertension characterized by hyperkalaemia and hyperchloraemic acidosis despite a normal glomerular filtration rate. To date, three different loci have been identified, on chromosomes 1, 17 and 12.

OBJECTIVE

To test for genetic linkage between the three FHH loci and three new affected kindreds.

DESIGN AND METHODS

Clinical, biological and genetic analyses were made of three kindreds, including 11 affected individuals among 25 members. Genotyping was performed using four series of microsatellite markers spanning the chromosomes 1, 17 and 12 loci, and the thiazide-sensitive Na-Cl cotransporter (SLC12A3) gene.

RESULTS

Segregation of the trait in each kindred was compatible with an autosomal transmission, the affected individuals displaying reasonably consistent biochemical abnormalities and the expected variability in arterial hypertension. Multipoint linkage analysis excluded linkage with the four candidate loci in kindreds 1 and 2, but not with the chromosome 1 locus in kindred 3.

CONCLUSION

These results demonstrate further genetic heterogeneity and that a fourth gene is responsible for FHH in at least two unrelated kindreds. They suggest a variety of molecular defects leading to FHH.