The Isomer Ratios of Urinary Coproporphyrins I-IV are pH-Dependent)

K. Jacob, E. Egeler, B. Hennel, P. Luppa, D. Neumeier

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The percentage of porphyrinogens äs related to total porphyrin excretion was determined in the urine of healthy subjects. Acidic urines (pH 5.0 to5.9) contained 62.9 + 10.7% (x ± s, N = 11) porphyrinogens, whereas in neutral urines (pH 6.0 to 7.2) a somewhat lower percentage (51.2 + 15.3%, N = 11) wasdetected. However, there was no significant differencebetween the mean porphyrinogen Contents of acidic and neutral urines. Evidence was found for a previously unreported pH-dependent influence on the isomer ratios of urinary coproporphyrins I and III. Acidic urines (N = 18) fromhealthy subjects showed significantly higher percentages, of isomer I (27.1 + 6.4%), isomer II (2.7 ±1.1%), and isomer IV (5.0 ± 1.3%) äs compared to respective values from neutral urines (22.2 +5.1% isomer I, 0.6 ± 0.6% isomer II, and 1.5 + 1.3% isomer IV; N = 16, p < 0.001). Conversely, the percentage of isomer III was markedly lower in acidic urines than in neutralurines (65.1 + 7.9% vs. 75.9 + 5.4%; p < 0.001). The same relationship was confirmed in an individual subject by analysis of a series of urines(N = 13) with pH values ranging from 5.4 to 7.3. Theseresults point to the possibiiity that the atypical coproporphyrin isomers II and IV are predominantly formedby an increased isomerization rate of coproporphyrinogens under acidicintravesical conditions.

Original languageEnglish
Pages (from-to)115-120
Number of pages6
JournalClinical Chemistry and Laboratory Medicine
Issue number2
StatePublished - 1991
Externally publishedYes


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