Neurohormonal factors in heart failure.

Currently there are 4 to 5 million people with congestive heart failure in the United States. They consume greater than 7% of the total health care dollar of which a significant portion is directly related to hospitalization expenses alone. Most patients with chronic congestive heart failure can be managed efficiently outside the hospital setting by the proper use of nonpharmacologic therapies. Neurohormonal pathways have a significant impact on the progression of congestive heart failure. Medications, which include alpha-blockers, beta-blockers, digoxin, spironolactone, and diuretics, now can block, modify, or manage most of these neurohormonal effects, and therefore, have a stabilizing effect on the patient with congestive heart failure. Understanding the physiology and medications involved for optimal treatment of congestive heart failure is a must to ensure the quality of life that these patients deserve.

Mineralocorticoid receptor antagonists: the evolution of utility and pharmacology.

For more than 30 years after the discovery of aldosterone, scientists believed that its sole site of action was at epithelial tissues, most notably the kidney, where it mediated the transport of Na and K. It was soon recognized aldosterone contributed to several diseases by causing edema. Armed with this information, scientists set out more than 30 years ago to develop an antagonist of the mineralocorticoid receptor for the treatment of edematous states. From this effort, spironolactone (Aldactone was discovered. Spironolactone acts functionally as a competitive inhibitor of the mineralocorticoid (aldosterone) receptor, and although spironolactone is an effective mineralocorticoid receptor antagonist, it is not without limitations. These limitations include unwanted progestational and antiadrogenic side effects that limit its use in the chronic treatment of disease. In addition to its actions at the collecting tubule, aldosterone can participate in pathophysiology by actions at the heart, vasculature, and kidney, and it is likely that the most significant contributions to cardiovascular disease are due to actions at these sites rather than those related to Na and water retention. This is underscored by the recent clinical results from the RALES-004 Trial in which treatment with Aldactone demonstrated a significant benefit on mortality in patients with severe heart failure. The limited utility of spironolactone owing to the aforementioned steroid-related side effects has been especially frustrating, given the newly recognized role of aldosterone in cardiovascular disease. To obviate these limitations, eplerenone is currently being developed by Searle. Eplerenone is a competitive antagonist of the mineralocorticoid receptor that takes advantage of replacing the 17alpha-thoacetyl group of spironolactone with a carbomethoxy group, conferring excellent selectivity for the mineralocorticoid receptor over other steroid receptors. The pharmacological profile of eplerenone positions it to be an effective and selective mineralocorticoid receptor antagonist.

Electrolyte economy and its hormonal regulation in congenital chloride diarrhea.

The economy of Cl-, K+, and Mg++, extracellular volume (ECV) and plasma volume, and the role of hyperreninemia and hyperaldosteronism were explored in 22 patients with congenital chloride diarrhea. Stool volume was in significant correlation with its Cl-, Na+ and K+ content, the correlation being significantly better with Cl- content than with the Na+ content. Low fecal Cl- concentrations were seen in chronic hypochloremic contraction, but acute episodes did not cause reduction of fecal Cl- concentration from the basal level of 140--150 mmol/liter. The adequate condition (defined as normal serum electrolyte concentrations and bl;od pH, and presence of Cl- in urine) was associated with high total exchangeable Cl- and ECV. This excess Cl- and ECV roughly equalled the high daily fecal amount of Cl- and volume. Reduced ECV was accompanied by high renin activities and hyperaldosteronism, but in the adequate condition these were normal. Hyperaldosteronism caused a decrease in urinary Na+-K+ ratio and, after the age of 2--6 months, in the fecal Na+-K+ ratio. Total exchangeable K+ was normal in the adequate condition. No Mg++ depletion was present, although the patients lack Mg++ substitution. The adequate condition could be maintained with an oral supplement of NaCl, KCl and water.