Saturnine Gout: Lead-Induced Formation of Guanine Crystals

Intravenous injection of a sublethal dose of lead acetate into a domestic pig resulted in a 4.5-fold increase of guanine in the urine, indicating an impairment in the conversion of guanine to xanthine. This impairment is probably due to the inhibition of guanine aminohydrolase (guanase), since the activity of this enzyme is inhibited by Pb$^{2+}$ (the inhibition constant being 3.0 × 10$^{-6}$M). Postmortem histological examination revealed concretions of crystalline material in the epiphyseal plate of the femoral head. Extraction of the section containing the concretions showed that they were guanine. The relation of these findings to saturnine gout is discussed.