Determination of urinary uroporphyrin by a direct extraction method

Partition of porphyrins between cyclohexanone and aqueous sodium acetate as a function of pH. Determination of uroporphyrin and of hydrophilic porphyrin conjugates

1. The partition of uroporphyrins I and III, coproporphyrins I and III, haematoporphyrin IX, porphyrin c and a hydrophilic porphyrin-peptide fraction from variegate-porphyria faeces has been studied in systems of equal volumes of cyclohexanone and sodium acetate buffers of varying pH and concentration. 2. The concentration of acetate in the aqueous phase has little effect on the partition of porphyrin c, but markedly influences that of uroporphyrin. At 50% acetate saturation and pH4.5, only 5% enters the cyclohexanone phase whereas 60% of porphyrin c is extracted under similar conditions. 3. This circumstance forms the basis of a method for the determination of hydrophilic porphyrin-peptides in variegate-porphyria urine. Its reliability has been checked in model experiments. 4. At pH1.5 and an aqueous phase half-saturated with sodium acetate, an equal volume of cyclohexanone removes 95-97% of uroporphyrin and about 55% of porphyrin c. Uroporphyrin may therefore be determined as a second step in the method. 5. For the routine determination of uroporphyrin in systems free from other hydrophilic porphyrins, cyclohexanone extraction may be performed at any pH in the range 1.0-3.0.

Free erythrocyte protoporphyrin (FEP) and zinc protoporphyrin (ZnP) as biological parameters for lead poisoning

Lamola et al. (1974) reported that free erythrocyte protoporphyrin (FEP) is not present as free type protoporphyrin ( FPP ) but rather is chelated with zinc in lead poisoning and iron deficiency anemia. In our fluorometric study of FEP and zinc protoporphyrin ( ZnP ) in erythrocytes of lead-poisoned rabbits and lead workers, the co-existence of ZnP and FPP was observed in the severe stage of acute lead poisoning in rabbits. The ratio of ZnP to FEP in erythrocytes decreased with the progress of lead intoxication, and the amount of FPP was greater than that of ZnP in the severe stage of intoxication. This FPP accumulated in the erythrocytes was easily converted to ZnP by incubation of the hemolysate with zinc. On the other hand, increased protoporphyrin (PP) in bone marrow was present as FPP in lead intoxication. From these results, ZnP in peripheral erythrocytes is considered to be a secondary product, not a primary one. Therefore, the determination of total FEP ( FPP + ZnP ) by the acid solvent extraction method might be more reasonable than using ZnP -determination as the biological parameter of lead poisoning. We propose that erythrocyte porphyrin in lead intoxication should be expressed as FEP, not as ZnP , for the parameter. The present study also suggests that the form of erythrocyte FPP in erythropoietic protoporphyria (EPP) patients is a little different from that in lead-poisoning patients, because of its high chelation reactivity with zinc.

The effect of fluroxene [(2,2,2-trifluoroethoxy)ethane] on haem biosynthesis and degradation

Acute fluroxene treatment of male Wistar rats decreases the amounts of hepatic microsomal cytochrome P-450 and haem, increases the activities of hepatic delta-aminolaevulinate synthase and haem oxygenase, and increases the amounts of haem precursors (delta-aminolaevulinate and porphobilinogen) in the urine. All of the above effects of fluroxene are enhanced by pretreatment of the experimental animals with 3-methylcholanthrene and phenobarbital. The amounts of porphyrins in the urine and faeces were generally unaffected by acute fluroxene treatment of uninduced or 3-methylcholanthrene- or phenobarbital-induced Wistar rats. 2,2,2-Trifluoroethyl ethyl ether, the saturated analogue of fluroxene, did not affect the amounts of hepatic cytochrome P-450 and haem, the amounts of any of the haem precursors in the urine or faeces, or the activity of hepatic haem oxygenase in phenobarbital-induced male Wistar rats. The amounts of hepatic cytochrome P-450 and haem and of the haem precursors in urine and faeces, and the activity of delta-aminolaevulinate synthase, were generally not altered by acute fluroxene treatment of uninduced male Long-Evans rats. Chronic treatment of Wistar rats with fluroxene resulted in small increases in the amounts of delta-aminolaevulinate and porphyrins in urine. The amounts of porphobilinogen in urine were elevated up to 2000%, whereas the amounts of the porphyrins in faeces were generally unaffected. After chronic fluroxene treatment, the activity of delta-aminolaevulinate synthase was increased, whereas the activity of uroporphyrinogen synthase was decreased. It is concluded that acute fluroxene treatment may affect haem biosynthesis and degradation by a mechanism similar to allylisopropylacetamide, namely by stimulating an atypical cytochrome P-450-dependent pathway for haem degradation. The effects of chronic fluroxene treatment on haem biosynthesis may be a consequence of this mechanism or a result of the inhibition by fluroxene of uroporphyrinogen synthase. Chronic fluroxene treatment of male rats affects the haem biosynthetic pathway in a manner similar to that seen in human genetic acute intermittent porphyria.

Lead poisoning in monkeys: functional and histopathological alterations of the kidneys

Ten monkeys (Macacus Irus) were given 0--15 mg of lead acetate (in drinking water) 6 days a week for 9 months. Two of the monkeys were also put on a low calcium diet with 6 mg of lead acetate/day. The blood lead level usually increased from the third month according to the dose of lead ingested and more quickly in monkeys deprived of calcium. Some of the monkeys showed signs of alteration in protein glomerular filtration and/or proximal tubular reabsorption. Studies using optical and electron microscopy showed distinct pathological changes in the proximal tubular epithelium where heavy deposits of lead were seen in the nuclei.

Uroporphyrinogen III cosynthase-deficient mutant of Salmonella typhimurium LT2

A new type of heme-deficient mutant of Salmonella typhimurium LT2 was isolated using neomycin. The mutant, designated as strain SASY74, accumulated uroporphyrin I and coproporphyrin I. Extracts of the mutant converted 5-aminolevulinic acid to uroporphyrin I. Extracts of the mutant SASY74 and of the uroporphyrinogen synthase-deficient mutant SASY32 complemented each other and converted, when incubated together, 5-aminolevulinic acid to protoporphyrin. This finding excludes the possibility that uroporphyrinogen I synthase in strain SASY74 is deficient in its cosynthase-binding ability. Hence, the most probable explanation for the accumulation of uroporphyrin I and coproporphyrin I by the mutant is the lack of the uroporphyrinogen III cosynthase activity. This mutant is the first isolated in bacteria with such deficiency, and the mutation is analogous, as far as porphyrin synthesis is concerned, to human congenital porphyria. Mapping of the corresponding gene (hemD) by conjugation and P22-mediated transduction suggests the following gene order on the chromosome: ilv....hemC, hemD, cya....metE. The hemC and hemD genes are probably adjacent; this is the first case in which two hem genes of Enterobacteriaceae are contiguous on the chromosomal map.

Uroporphyrin-accumulating mutant of Escherichia coli K-12

An uroporphyrin III-accumulating mutant of Escherichia coli K-12 was isolated by neomycin. The mutant, designated SASQ85, was catalase deficient and formed dwarf colonies on usual media. Comparative extraction by cyclohexanone and ethyl acetate showed the superiority of the former for the extraction of the uroporphyrin accumulated by the mutant. Cell-free extracts of SASQ85 were able to convert 5-aminolevulinic acid and porphobilinogen to uroporphyrinogen, but not to copro- or protoporphyrinogen. Under the same conditions cell-free extracts of the parent strain converted 5-aminolevulinic to uroporphyringen, coproporphyrinogen, and protoporphyrinogen. The conversion of porphobilinogen to uroporphyrinogen by cell-free extracts of the mutant was inhibited 98 and 95%, respectively, by p-chloromercuribenzoate and p-chloromercuriphenyl-sulfonate, indicating the presence of uroporphyrinogen synthetase activity in the extracts. Spontaneous transformation of porphobilinogen to uroporphyrin was not detectable under the experimental conditions used [4 h at 37 C in tris(hydroxymethyl)aminomethane-potassium phosphate buffer, pH 8.2]. The results indicate a deficient uroporphyrinogen decarboxylase activity of SASQ85 which is thus the first uroporphyrinogen decarboxylase-deficient mutant isolated in E. coli K-12. Mapping of the corresponding locus by P1-mediated transduction revealed the frequent joint transduction of hemE and thiA markers (frequency of co-transduction, 41 to 44%). The results of the genetic analysis suggest the gene order rif, hemE, thiA, metA; however, they do not totally exclude the gene order rif, thiA, hemE, metA.