Spot urine porphyrins/creatinine ratio profile of healthy Brazilian individuals adjusted for personal habits

Abstract

Changes in urinary porphyrin excretion may be the result of hereditary causes and/or from environmental or occupational exposure. The objective of this study was to measure the amount of some porphyrins in spot urine samples obtained from volunteers randomly selected from a healthy adult population of São Paulo with a sensitive HPLC method and to estimate normal ranges for a non-exposed population. Spot urine samples were collected from 126 subjects (both genders, 18 to 65 years old) not occupationally exposed to porphyrinogenic agents. Porphyrin fractions were separated on RP-18 HPLC column eluted with a methanol/ammonium acetate buffer gradient, pH 4.0, and measured fluorometrically (excitation 405 nm/emission 620 nm). The amount of porphyrins was corrected for urinary creatinine excretion. Only 8-carboxyl (uro) and 4-carboxyl (copro) porphyrins were quantified as μg/g creatinine. Data regarding age, gender, occupational activities, smoking and drinking habits were analyzed by Mann-Whitney and Kruskal-Wallis tests. Uroporphyrin results did not differ significantly between the subgroups studied. Copro and uro + copro porphyrins were significantly different for smokers (P = 0.008) and occupational activities (P = 0.004). With respect to alcohol consumption, only men drinking >20 g/week showed significant differences in the levels of copro (P = 0.022) and uro + copro porphyrins (P = 0.012). The 2.5-97.5th percentile limit values, excluding those for subjects with an alcohol drinking habit >20 g/ week, were 0-20.8, 11.7-93.1, and 15.9-102.9 μg/g creatinine for uro, copro and uro + copro porphyrins, respectively. These percentile limit values can be proposed as a first attempt to provide urinary porphyrin reference values for our population, serving for an early diagnosis of porphyrinopathies or as biomarkers of exposure to porphyrinogenic agents.