Adsorption of natriuretic factors in uremia

Patients with end-stage renal disease have a deranged sodium and water homeostasis leading to chronic volume overload. Atrial natriuretic peptides (ANPs) are circulating hormones that are involved in the regulation of volume homeostasis, blood pressure control, and electrolyte balance. In hemodialysis patients plasma ANPs are highly elevated and decrease during the dialysis session when fluid is removed. However, hemodialysis treatment never corrects the defect in the metabolism of these peptides and their circulating concentrations do not return to levels found in healthy controls. Besides uremia and chronic volume overload, other factors such as cardiac dysfunction or hypertension may contribute to the elevated plasma concentrations of ANPs. ProANP fragments which derive from the N-terminus of the ANP prohormone have been also found in the circulation and they have biological functions similar to alpha-ANP (ie, the C-terminus of the prohormone). The proANP peptides proANP(1-30), proANP(31-67), and proANP(1-98) are increased in patients undergoing regular hemodialysis treatment, but their decrease during the dialysis procedure is less pronounced than for alpha-ANP or cyclic GMP. Cellulose triacetate dialyzer membrane material lowered the plasma concentrations of proANP(1-30), proANP(31-67), and proANP(1-98) significantly more than polysulfone, whereas alpha-ANP and cyclic GMP were not differently affected. Aside from a variety of factors that influence circulating natriuretic factors in the uremic patient, there is evidence for differences in dialyzer membrane adsorption of these peptides which speculatively may be linked to dialysis-associated symptoms.