PSEUDOURIDINE EXCRETION IN HEALTHY-SUBJECTS AND ITS ACCUMULATION IN RENAL-FAILURE

Pseudouridine (PSI) is a unique nucleoside accumulated in the sera of renal failure (RF) patients. Surprisingly data on its excretion are lacking. To get an overview, the PSI-serum level and urinary excretion were investigated in 73 healthy subjects (C), 16 patients not on dialysis (ND) and 12 hemodialysis patients (D). It was found: (a) PSI-accumulates in the sera of both ND and D patients. An inverse power correlation fits best with the relationship between serum-PSI and the clearance of endogenous creatinine (C(Cr)). The amount of PSI-filtered in glomeruli of ND patients increases while it remains practically unchanged in D patients. However, the PSI-filtration load of residual nephrons increases with the decreasing C(Cr) as a consequence of its increased serum concentration. (b) Both PSI-net resorption and secretion have been found in C subjects. The increased PSI-resorption diminishes the necessary increase of PSI-urinary excretion both in ND and D patients. The increase of PSI-resorption is marked if calculated on residual nephrons. (c) The slightly decreased PSI-excretion excludes the participation of its increased synthesis in its accumulation in RF. It is concluded that PSI-accumulation in RF is caused by the impairment of its kidney excretion and the increased PSI-resorption participates markedly in its retention.