Metabolic fate of intravenously administered N-acetylneuraminic acid-6-14C in newborn piglets.

BACKGROUND Sialic acid (N-acetylneuraminic acid), a component of gangliosides and sialylglycoproteins, may be a conditional nutrient in early life because endogenous synthesis is limited. The aim of this study was to investigate the metabolic fate of intravenously administrated N-acetylneuraminic acid-6-14C (sialic acid) in piglets. METHOD Three-day-old male domestic piglets (Sus scrofa) were injected via the jugular vein with 5 microCi (11-12 x 10(6) cpm) of N-acetylneuraminic acid-6-14C (specific activity of 55 mCi/mmol). Blood samples were collected at regular intervals over the next 120 min. The organs were then removed and the urine collected for determination of residual radioactivity. RESULTS Within 2 min of injection, 80% of the activity was removed from the blood and by 120 min the remaining activity approached 8%. At 120 min, the brain contained significantly more radioactivity (cpm/g tissue) than the liver, pancreas, heart and spleen, but less than the kidneys. Within the brain, the percentage of total injected activity was highest in the cerebrum (0.175 +/-0.008) followed by the cerebellum (0.0295 +/-0.006, p=0.00006) and the thalamus (0.029 +/- 0.006, p =0.00003). CONCLUSIONS An exogenous source of sialic acid is capable of crossing the blood-brain barrier and being taken up into various tissues. The findings suggest that dietary sources of sialic acid may contribute to early brain development in newborn mammals.