[Role of the atria in controlling body fluids]

The atria play a major role in the regulation of body fluids. Since the work of Henry and col., techniques of atrial distention have shown the existence of volume receptors which perceive the fulness of blood volume, the left atrium in particular. When blood volume increases, receptors originate a neuro-humoral reflex in which the afferent path would be the vagus nerve, the hypotalamus would be the center, and the efferent path would be the inhibition of the hypophysis ADH secretion, provoking a decreased water reabsorption and, consequently, diuresis. This mechanism would have precedence over the osmotic regulation. Added to the investigations of the authors, these experiments also point to an increased sodium excretion, for which release of a natriuretic factor in a non-determined site was claimed as responsible. In 1981, de Bold and col. reported a hormone produced in atrial cardiocites (ANF) that would be released upon stretching of the atrium and that would act upon the nephron through different mechanisms to cause deep diuresis and natriuresis. This publication gave origin to numerous investigations. The formula of the responsible peptide was determined. The hormone was sinthesized and the pharmaceutical industry launched many synthetic products. The physiologic and physiopathologic implications of this discovery and the therapeutic potential of these synthetic derivatives are discussed.