The atrial natriuretic factor in mild essential hypertension.

Small granules are seen around the poles of the nuclei of most cells of the heart atria of all mammalian species including men. They contain proteinaceous material and their number varies with sodium and water balance (1). Their significance became clear with the observation in 1981 of de Bold, et al. that crude homogenates of rats' atria, when injected into normal rats, produced a rapid, massive and short lasting diuresis, natriuresis, and vasorelaxation, with a decrease in mean arterial pressure (2). Since this finding, progress in this field has been extremely rapid. Several small peptides of varying length, but having the same core of 21 amino acids have been isolated by various groups. The major circulating form of atrial natriuretic factor (ANF) is a 28 amino acid peptide (Ser 99-Tyr 126) both in rat and in man (3-5). This peptide shows almost complete homology between various species, the only difference being a methionine group in position 110 in cattle, dog, and man instead of the isoleucine found in rat, mouse and rabbit (Fig. 1). The major effects of ANF (or more appropriately CNF, cardiac natriuretic factor, because of the presence of the ANF gene and of mRNA in heart ventricles [6-8]) are a) renal, with a marked diuresis and natriuresis resulting mostly from an increased glomerular filtration rate and filtration fraction, b) vascular, resulting in selective vasodilatation in some territories and not in others, c) adrenal, with inhibition of aldosterone liberation, d) cerebral with important concentrations of immunoreactiveANF in the AV3V region and also in the retina and olfactory bulb. Studies of ANF in relation to human hypertension are therefore relevant, especially so since previous work by Garcia and our group in rats (9-11) and others in dogs, especially Kleinert, et al. (12), Granger, et al. (13), and Seymour, et al. (14) have shown that administration of ANF either by bolus injection or by continuous infusion, results in a significant decrease in blood pressure in hypertensive rats (2K-1C, 1K-