[Aldosterone excretion in patients with essential hypertension after variable sodium loading (author's transl)]

[Atrial natriuretic peptide and its significance for arterial hypertension]

Atrial natriuretic peptide is a recently discovered cardiac hormone with natriuretic, vasodilatory and hypotensive activities. The role of this hormone in the pathophysiology of hypertension is of particular interest. In contrast to an earlier concept, a deficiency of the atrial peptide could not be found in animal models of hypertension or in patients. ANP plasma levels were elevated in SHR with accelerated hypertension, in salt-sensitive Dahl rats, in rats with DOCA-salt-hypertension and in animals with renovascular hypertension. Elevated ANP levels under these conditions can be explained by an expansion of the intravascular volume or by an elevated atrial wall stretch induced by the hypertension itself. In patients with primary hypertension, plasma levels of the peptide are raised in some patients and are normal in others. Plasma ANP levels correlate with age, blood pressure and signs of left ventricular hypertrophy. A negative correlation is described between ANP and renin. Measurement of plasma ANP levels does not allow a differentiation between primary and secondary forms of hypertension. Elevated ANP levels are also found in primary hyperaldosteronism and in renal failure. Stimulation of ANP secretion by physical exercise and dietary salt loading is maintained in hypertension. Infusion of 1-28-hANP leads to a reduction in systemic arterial pressure in normotensives and hypertensives. The natriuresis induced by exogenous ANP is more pronounced in hypertensives. Stimulation of endogenous ANP secretion does not prevent the rise in blood pressure possibly due to a reduction in ANP receptors in target tissues.

Aldosterone, sodium and potassium in essential hypertension

Eighty-five patients with essential hypertension received a restricted sodium diet for 10 days. During the last 5 days sodium intake was increased by oral administration of an additional 300 mmol of NaCl. At the end of both periods blood pressure, plasma and urinary concentration of Na and K, and 24-hour secretion rate of aldosterone (ASR) were determined. ASR in the hypertensives was after NaCl loading slightly higher than that in 21 normotensive controls. Aldosterone secretion rates were highest in patients with the lowest plasma K levels after loading with NaCl. This relationship between ASR and potassium was not found after NaCl restriction. After both NaCl restriction and NaCl loading the plasma K concentrations were lowest in patients with the highest mean arterial pressures. From statistical analysis of the relations between plasma Na, plasma K, ASR and mean arterial pressure it seems highly unlikely that aldosterone plays a prime role in the relation between the height of the blood pressure and the concentration of plasma K in essential hypertension. Our data seem in line with the presence of a primary abnormality in electrolyte metabolism in essential hypertension and slight aldosteronism after salt loading as its sequela.