No abstract

The accumulation in blood plasma and efficiency of hemodialysis of pyrimidine compounds (orotic acid, orotidine, pseudouridine, uridine, thymine) as well as uric acid and creatinine in 23 patients with chronic renal failure (CRF) was investigated. As a reference, the analysis of the above metabolites in the plasma of 30 healthy volunteers was performed. Among examined compounds, pseudouridine possessed the highest capability of accumulation in blood plasma (25 times higher concentration than physiological). It coincided with the lowest efficiency of pseudouridine hemodialysis (44%) and the longest T_½ (relative to creatinine) in plasma. A significant linear correlation (r = 0.81, p < 0.001) between efficiency of creatinine and pseudouridine hemodialysis was calculated. The concentration of orotic acid in the blood plasma of patients before hemodialysis exceeded 14 times its level in healthy subjects; the inhibition of uric acid synthesis by allopurinol in dialyzed patients was accompanied by enlargement of orotidine and orotate accumulation in blood plasma. Extremely high plasma concentration of examined pyrimidines remaining elevated after hemodialysis creates an additional hazard for tissue metabolism and health of patients with CRF.

The blood plasma concentration of pseudouridine was estimated in 104 healthy adult subjects, and 108 patients suffering from malignant proliferative diseases. The HPLC method for simultaneous determination of pseudouridine and creatinine was applied.The average physiological concentration of pseudouridine in blood plasma was 2.43 ± 0.97 μπιοί -I" 1 or 29.15 + 7.40 mmol · mol" 1 creatinine. The physiological urinary excretion of pseudouridine was 14.32 ± 5.20 μπιοί -24h" 1 · kg~°· 75 or 19.60 + 5.22 mmol -mol" 1 creatinine. Renal clearance of pseudouridine and endogenous creatinine were 4.04 + 0.99 and 5.50 ± 1.46ml -kg" 075 , respectively. A positive correlation (r = 0.55, P < 0.01) was found between age (in the range 20 -92 years) and blood plasma pseudouridine concentration (μιηοΐ · I" 1 ). By expressing plasma pseudouridine in relation to plasma creatinine, the apparent influence of non-metabolic factors (age, renal insufficiency, blood dilution) on the plasma pseudouridine concentration were largely excluded.Among haematological proliferative diseases the highest values of plasma pseudouridine concentrations were observed in chronic lymphocytic leukaemia (8.19 μπιοί-I" 1 ; 54.9 mmol -mol"" 1 creatinine) and multiple myeloma (7.02 μπιοί · I" 1 ; 52.5 mmol · mol~J creatinine). In multiple myeloma, but not in chronic lymphocytic leukaemia, the plasma pseudouridine concentration depended on the clinical stage. A lower, but still significant response in non^Hodgkin's lymphoma was noted (4.03 μπιοί · I" 1 ; 40.88 mmol · mol" 1 creatinine).A significant increase of the plasma pseudouridine concentration was characteristic of adenocarcinomas of the large intestine, and it occurred in the early stages of malignant growth. In patients with lung cancer the plasma pseudouridine concentration was elevated only in advanced cases with metastases. The increased pseudouridine concentration was evident in all examined cancers of the urogenital system: cancer of the urinary bladder, cancer of the kidney, cancer of the prostate, and cancer of the testis.It is concluded that the determination of pseudouridine in blood plasma, particularly in relation to creatinine, is a valuable biochemical m rker of accelerated turnover rate of nucleic acids associated with neoplastic growth. ') This study was supported by a grant from the Ministry of National Education.

The HPLC method for the simultaneous determination of urinary neopterin, pseudouridine, and creatinine allows a rapid evaluation of the activation state of cell-mediated immunity, and the stimulation of whole-body rRNA + tRNA turnover, associated with malignant growth ..Urinary neopterin and pseudouridine concentrations in healthy subjects amounted to: 106.6 ± 34.6 μιηοΐ/mol creatinine, and 19.6 ± 5.2 mmol/mol creatinine (x ± SD), respectively. The increase of neopterin excretion in patients with haematological neoplasms ranged from 146% in Hodgkitfs disease to 534% in non-Hodgkin's lymphoma, whereas the increase in cancer cases ranged from 95% in adenocarcinoma of the gaster to 741% in hepatocellular carcinoma. The changes in pseudouridine excretion were much less pronounced: 63% in non-ffodgkin's lymphoma and 120% in carcinoma of the urinary bladder. The correlation coefficient between neopterin and pseudouridine was relatively low (r = 0.43), although statistically significant (P < 0.01). In the case of several neoplasms e.g. Hodgkin's disease, polycythaemia vera, and adenocarcinoma of the gaster, neopterin was significantly elevated, whereas pseudouridine remained at a normal concentration. There was a positive relationship between the stage of the disease (primary focus, regional metastases, dissemination) and urinary concentration of pseudouridine in patients with adenocarcinoma of the large intestine. In the same patients the increase of neopterin excretion was noticed both in early and advanced stages, with the highest values in disseminated disease.

The renal orotate clearance (C, , , , ) in control (infusion of 0.9 % NaCl into jugular vein) andhyperammonaemic (infusion of NH,CI in a dose of 20 p o l . kg-' . min-') conditions in the same sheep was investigated. C,,o,,, was compared with Cinubnr a valid index of glomerular filtration rate (GFR). Turnover time (T) of orotate in blood plasma, GFR, and C , , , in control conditions was 4.5 min, 5.5 cm'/min. kg".", and 15.7cm3/ min. kg0.75, respectively. Ammonia reduced To,,,,, to 4.0 min, and increased GFR and C, , , , .to 6.9 cm3 / min * kgO" and 20 cm' / min . kg".", respectively. The mechanism of renal orotate excretion, and its response to peripheral hyperammonaemia are discussed.