ENDOGENOUS PURINE AND PYRIMIDINE DERIVATIVE EXCRETION IN PREGNANT SOWS

The present experiment was carried out to study the endogenous losses of purine and pyrimidine derivatives from pregnant sows. Three pregnan t and three non-pregnant Large White x Landrace sows were fed on a pur ine-free diet composed of starch, glucose, sucrose and vegetable oil, with casein as the protein source. The experiment began, for the six a nimals, after diagnosis of pregnancy and was divided into six 12 d per iods. Urine was collected during the first 3 d of each experimental pe riod by means of a urethral catheter for determination of allantoin, u ric acid, xanthine, hypoxanthine and pseudouridine concentrations. In the absence of dietary nucleic acids (NA), allantoin and, as a consequ ence, excretion of total purine derivatives (PD) decreased significant ly to a constant value (128.3 (SE 7.07) mu mol/kg metabolic live weigh t (W-0.75) per d), an amount assumed to represent endogenous excretion . Excretion of uric acid (38.7 (SE 2.15) mu mol/kg W-0.75 per d), hypo xanthine (21.0 (SE 2.58) mu mol/kg W-0.75 per d) and xanthine (11.2 (S E 0.83) mu mol/kg W-0.75 per d) were not affected by the experimental treatment, although there was a significant decrease in hypoxanthine e xcretion in pregnant sows (from 25.5 to 5.2 mu mol/kg W-0.75 per d) co mpared with non-pregnant sows (from 26.7 to 44.8 mu mol/kg W-0.75 per d). Creatinine excretion was not affected by pregnancy and was used as an internal urinary marker. Purine excretion, either expressed as mu mol/kg W-0.75 per d or as the ratio PD:creatinine, was not affected by experimental treatment, although an apparent increase in pseudouridin e excretion, a modified unsalvageable catabolite of RNA-pyrimidine, wa s found in late pregnancy (3.6 v. 5.2 mol/100 mol creatinine in non-pr egnant sows compared with pregnant sows at 102 d collection).