Excretory and storage purines in the Anomuran land crab Birgus latro; guanine and uric acid

Birgus latro excretes nitrogenous waste as a mixture of urate and guanine and not predominantly urate as believed previously. The presence of guanine in faeces was confirmed by enzymatic derivatisation of guanine to xanthine with guanase. This is the first report of significant excretion of guanine outside the Chelicerata. The ratios of urate to guanine within the excreta of animals in field situations (natural diets) and in the laboratory (a range of artificial diets) were 3:2. Rates of excretion of both urate and guanine increased when experimental crabs were fed an artificial diet high in nitrogen. Significant amounts of guanine were also measured in tissues of B. latro, but only urate was present in equivalent tissues of the closely related species Coenobita brevimanus. Coenobita brevimanus did not excrete any significant amount of purines with the faeces.

The influence of allopurinol on urinary purine loss after repeated sprint exercise in man

The influence of allopurinol on urinary purine loss was examined in 7 active male subjects (age 24.9 ± 3.0 years, weight 82.8 ± 8.3 kg, V˙o₂peak 48.1 ± 6.9 mL · kg⁻¹ · min⁻¹). These subjects performed, in random order, a trial with 5 days of prior ingestion of a placebo or allopurinol. Each trial consisted of eight 10-second sprints on an air-braked cycle ergometer and was separated by at least a week. A rest period of 50 seconds separated each repeated sprint. Forearm venous plasma inosine, hypoxanthine (Hx) and uric acid concentrations were measured at rest and during 120 minutes of recovery from exercise. Urinary inosine, Hx, xanthine, and uric acid excretion were also measured before and for 24 hours after exercise. During the first 120 minutes of recovery, plasma Hx concentrations, as well as the urinary Hx and xanthine excretion rates, were higher (P < .05) with allopurinol compared with the placebo trial. In contrast, plasma uric acid concentration and urinary uric acid excretion rates were lower (P < .05) with allopurinol. The total urinary excretion of purines (inosine + Hx + xanthine + uric acid) above basal levels was higher in the allopurinol trial compared with placebo. These results indicate that the total urinary purine excretion after intermittent sprint exercise was enhanced with allopurinol treatment. Furthermore, the composition of urinary purines was markedly affected by this drug.