N-terminal fragments of the proatrial natriuretic peptide in plasma and urine of kidney graft recipients

Background. Successful kidney transplantation normalizes elevated proatrial natriuretic peptide (proANP) plasma concentrations of renal failure patients in the early posttransplant period. We evaluated plasma and urinary proANP fragments in the late posttransplant period. Methods. Immunoreactive proANP(1-30) and proANP(31-67) were determined in 389 renal transplant (Rtx) recipients in the long-term, follow-up period and in 16 healthy controls. Results. Rtx recipients had significantly higher concentrations of proANP(1-30) and proANP(31-67) in both plasma and urine than healthy controls. Although their graft function was normal, all of these long-term Rtx recipients were taking glucocorticoids, which increase proANP(1-30) and proANP(31-67) in the circulation to the extent found in this investigation. Two-thirds of these recipients were also talking cyclosporine, which also increases atrial peptides. Urinary proANP(31-67) was significantly higher than urinary proANP(1-30); 5.5-fold in Rtx patients and 2-fold in controls. Deterioration of renal graft function was associated with a rise of plasma proANP(1-30) from 0.98 +/-0.66 to 6.28 +/-3.55 nmol/l (P<0.0001) and plasma proANP(31-67) from 1.81<plus/minus>1.04 to 7.89 +/-3.76 nmol/l (P<0.0001), Urinary excretion of proANP(1-30) increased from 0.27<plus/minus>0.34 to 5.96 +/-5.07 nmol/24 hr (P<0.0001) and proANP(31-67) from 1.45<plus/minus>0.85 to 12.23 +/-5.12 nmol/24 hr (P<0.0001). Also proteinuria enhanced plasma and urinary proANP fragments. Conclusions. ProANP(1-30) and proANP(31-67) of Rtx recipients are affected by immunosuppression, hypertension, renal failure, and proteinuria. One would have expected proANP(1-30) and proANP(31-67) not to normalize because of the glucocorticoids that they were receiving.