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A theoretical mode of action of aldosterone

1961; Elsevier BV; Volume: 1; Issue: 2 Linguagem: Inglês

10.1016/0022-5193(61)90047-9

1095-8541

Arthur J. Vander, Walter S. Wilde, Richard L. Malvin,

Hormonal Regulation and Hypertension

Aldosterone is the most important of known sodium-regulating hormones, although it is responsible for only a few per cent of total renal sodium reabsorption.In addition, aldosterone can increase renal excretion of hydrogen and potassium ions.That its renal effects are direct was first demonstrated by Barger, Berlin & Tulenko (1958) by unilateral renal artery injection of the hormone into normal and adrenalectomized dogs.Moreover, these investigators were able to demonstrate a complete dissociation of aldosterone's kaluretic and anti-natriuretic effects in the normal dog.Ganong & Mulrow (1958), using a similar technic, have also found a significant separation of these effects in the adrenalectomized dog.Thus the possibility that aldosterone accelerates transport systems exchanging sodium for hydrogen and potassium remains an unresolved question.Recently (Vander et al., 1958;1960), with the use of stop flow analysis technic (Malvin, Wilde & Sullivan, 1954, a distal site of action of aldosterone has been demonstrated.It is the purpose of this paper to describe a model for sodium transport and aldosterone activity based upon these findings. Site of Action of AldosteroneBy administration of an osmotic diuretic (mannitol) to the dog, very high rates of urine flow can be established.If during this period the ureter is clamped, intratubular pressure rises to equal net filtration pressure, at which point glomerular filtration ceases.During this period of stopped ureteral flow, the concentration of any substance in the intratubular fluid column will be changed along the nephron, depending upon how the individual segments handle this substance.The mannitol retards water reabsorption and provides a menstruum against which electrolyte concentrations may be changed.Upon release of occlusion, these concentra-