Genetics of primary hypertension

Pathogenesis and clinical physiology of hypertension

Significant advances have been made in understanding the pathogenesis and clinical physiology of primary hypertension. This article presents an overview of the physiology of normal blood pressure control and the pathophysiologic mechanisms that predispose individuals and populations to primary hypertension. The role of genetics, environment, and the gene-environment interaction is discussed. The spectrum of changes in physiologic states that result in chronic increases of arterial blood pressure are reviewed. The nature and characteristics of feedback loops and the primary modulating systems, the central and peripheral nervous systems, and circulating and tissue hormones are reviewed. The role of the endothelium of the artery and its production of endothelin, nitric oxide, angiotensin II, as well as other vasoactive substances in response to various stimuli, is also discussed. A unifying pathway for the development of hypertension and the practical implications for the prevention and control of hypertension are discussed.

Pathogenesis and clinical physiology of hypertension

Although the definitive cause of primary hypertension remains unknown, its pathogenesis and clinical history are relatively well understood. Genes, environment, and their interaction play crucial roles in the development of hypertension. Elevated blood pressure levels are maintained through alterations in multiple BP regulatory systems including the central and peripheral nervous system, renin-angiotensin-aldosterone system, renal mechanisms, structural and functional changes in the vascular wall and endothelium, and multiple feedback loops involving a wide spectrum of receptors and.

The contribution of inherited genotype to breast cancer

The etiology of breast cancer is complex, and is likely to involve the actions of genes at multiple levels along the multistage carcinogenesis process. These inherited genotypes include those that affect the propensity to be exposed to breast carcinogens, and those associated with breast tumorigenesis directly. In addition, inherited genotypes may influence response to breast cancer chemoprevention and treatment. Studies relating inherited genotypes with breast cancer incidence and mortality should consider a broader spectrum of genes and their potential roles in multistage carcinogenesis than have been typically evaluated to date. Understanding the role of inherited genotype at different stages of carcinogenesis could improve our understanding of cancer biology, may identify specific exposures or events that correlate with carcinogenesis, or target relevant biochemical pathways for the development of preventive or therapeutic interventions.

Losartan, an orally active angiotensin (AT1) receptor antagonist: a review of its efficacy and safety in essential hypertension

Losartan potassium, an angiotensin II receptor antagonist, is the first of a new class of agents to be introduced for the treatment of hypertension. In this review, we describe the clinical pharmacology of losartan, including its pharmacokinetics in healthy, male volunteers and special patient groups, such as the elderly, patients with liver disease and patients with renal impairment. We also review its pharmacodynamics, including safety and tolerability; specificity of action; and the effect of salt depletion. We then review the studies examining clinical efficacy and safety in hypertension.

Relationship between renal plasma flow response to angiotensin II and blood pressure in a population-based sample

OBJECTIVE

To assess whether interindividual variation in renal plasma flow or in its response to angiotensin II infusion is associated with interindividual differences in blood pressure in a population-based sample of 287 non-Hispanic whites (143 women and 144 men), aged 20-49.9 years.

METHODS

After seven days of eating a high-sodium diet (260 mmol/day), the renal plasma flow was determined by measuring the clearance of p-aminohippurate before and after infusion of 3 ng/kg per min angiotensin II. Multiple linear regression methods were used to assess whether measures of the renal plasma flow and of its response to angiotensin II infusion were predictive of systolic or diastolic blood pressures measured prior to administration of the high-sodium diet, on day 6 of the high-sodium diet, or during the renal clearance procedure on day 7 prior to angiotensin II infusion.

RESULTS

There was some evidence that measures of the renal plasma flow and of its response to angiotensin II infusion during the high-sodium diet were statistically significant predictors of measures of blood pressure in women; there was less evidence for this for blood pressures in men. Interindividual variation in measures of the renal plasma flow and of its response to angiotensin II infusion explained less than 10% of the interindividual variation in any measure of the blood pressure in both sexes.

CONCLUSION

These results suggest that interindividual variation in renal plasma flow ad in its response to angiotensin II infusion during a high-sodium diet will be of limited utility in elucidating the basis for interindividual differences in blood pressure.

Essential hypertension: could the basic defect be in blood supply of vasomotor centre?

Various factors have been implicated in the pathogenesis of essential hypertension, although the exact cause of essential hypertension is still unknown. In this paper it is suggested that the basic pathology in essential hypertension may be an inherited defect in the blood supply of that part of reticular formation of rostral ventrolateral medulla which contains the pressor area. The posited defect is one in which the arterial branch supplying blood to the above-mentioned pressor area of vasomotor center arises from an artery which is stenosed. The other branches of this stenosed artery supply adjacent areas of medullary reticular formation concerned with other neurological functions. Due to this stenosis there is ischaemia of the pressor area resulting in increased systemic arterial pressure. During stress, the blood requirement of adjacent areas of the reticular formation (whose function is still not clearly defined) may increase, thus further decreasing blood flow to vasopressor area and increasing the cerebral ischaemic response. After a prolonged time, this increased blood pressure can cause hyaline arteriolar nephrosclerosis in kidney, which may participate in the maintenance of elevated systemic arterial pressure.

Lipid lowering therapy leads to a reduction in sodium-lithium countertransport activity

Erythrocyte sodium-lithium countertransport (SLC) was measured in 17 patients with either combined hyperlipidaemia or hypercholesterolaemia before and after lipid lowering therapy. Before treatment SLC related to the serum triglyceride level and was increased in combined hyperlipidaemia. After treatment the SLC had returned to normal and the change in SLC was related to the change in serum triglyceride levels. Raised SLC is associated with essential hypertension but is not related to blood pressure. Therefore, the association of raised SLC with hyperlipidaemia and essential hypertension appears to have different underlying mechanisms.