A. Goldberg

TETRAETHYL-LEAD POISONING

Abstract Four cases of poisoning by tetraethyl lead are described. All the subjects had been simultaneously exposed to tetraethyl lead during the process of scaling a tank which had contained leaded petrol. Exposure was followed after a short interval by an illness in which mental symptoms were prominent. Blood-lead levels were raised to between 64·2 and 92·5 μg. per 100 g. Lead was found predominantly in the lipid fraction of blood. Urinary coproporphyrin-III excretion was slightly raised in only one case, and porphyrin-precursor excretion was normal. Erythrocyte-protoporphyrin excretion was slightly raised in the three most severe cases. There was a pronounced reduction in blood activity of δ-aminolaevulinic-acid dehydrase. Urinary lead excretion, which was initially high, was further increased by administration of D-penicillamine.

Value of Erythrocyte Protoporphyrin in the Diagnosis of Latent Iron Deficiency (Sideropenia)

THE erythrocyte content of free protoporphyrin does not normally exceed 40 p g . per IOO ml. erythrocytes (Cartwright, Huguley, Ashenbrucker, Fay and Wintrobe, 1948). In iron-deficiency anaemia, this level is greatly increased (Pagliardi, Prato, Giangrandi and Fiorina, 1959 ; Prato and Mazza, 1962; Heilmeyer and Clotten, 1962). Levels of erythrocyte protoporphyrin have not previously been studied in latent iron deficiency. Sideropenia is a term which refers to the stage of iron deficiency before frank anaemia has developed. Such sideropenic patients may be defined as those having haemoglobin levels between 12 and 13 g. per 100 ml., a saturation of the total iron-binding capacity less than 16 per cent, and an absence of stainable iron in the bone marrow. It is recognized that the tissue changes associated with iron deficienqsuch as atrophc glossitis, cheilosis and dysphagia, may occur before anaemia has developed (Waldenstrom, 193 8), and more recently Beutler, Larsh and Gurney (1960) have attributed such non-specific symptoms in women as chronic fatigue and ‘neurasthenia’ to tissue iron deficiency without anaemia. It would clearly be of value, in investigation of the sideropenic state, to have a reliable but simple means of confirming the presence of latent iron deficiency which would avoid the necessity for bone-marrow biopsy. The final step in the biosynthesis of haem involves the incorporation of iron into protoporphyrin and it was considered that the erythrocyte protoporphyrin level might be a sensitive index of early iron deficiency in the red cell. A study of free erythrocyte protoporphyrin levels has therefore been carried out in normal subjects, and in patients with latent iron deficiency and frank iron-deficiency anaemia, to determine the usefulness of t h s measure as a diagnostic test for sideropenia.

Controlled trial of haem arginate in acute hepatic porphyria.

A double-blind study comparing placebo and haem arginate was conducted in 12 patients with acute intermittent porphyria. 2 days after admission in attack patients were randomised to receive intravenous haem arginate 3 mg/kg per 24 h for 4 days or placebo. 9 patients were readmitted with a further attack and were given the alternative treatment. Before randomisation the paired attacks were of similar severity with respect to urinary porphobilinogen (PBG) excretion and clinical manifestations. With haem arginate the median PBG excretion of the 9 patients with two attacks (normal range 0-16 mumol per 24 h) fell significantly from 332 mumol per 24 h (range 137-722) on admission to a median lowest level of 40 (range 22-105). On placebo, median PBG excretion was 382 (range 196-542) on admission, falling to 235 (range 128-427). Median duration of admission after the start of treatment was 11 days (range 2-28) for placebo and 8 days (3-26) for haem arginate. Median total analgesic requirement between the start of treatment and discharge was 8150 mg pethidine equivalents (range 0-17,650) with placebo versus 6425 (range 50-20,650) with haem arginate. Phlebitis occurred in 5 patients on haem arginate and in 2 on placebo. Haem arginate effectively reduces porphyrin precursor overproduction in the acute porphyric attack but this reduction is not accompanied by striking resolution of the clinical manifestations of the attack.

Cytochrome Oxidase in Latent Iron Deficiency (Sideropenia)

THE tissue changes usually associated with iron-deficiency anaemia, such as atrophic glossitis, angular stomatitis and dysphagia, may occur during the stage of latent iron deficiency before anaemia has developed (Waldenstriim, 1938). More recently it has been suggested that nonspecific symptoms such as chronic fatigue, irritability and ‘neurosis’ in women may be due to tissue depletion of iron without accompanying anaemia (Beutler, Larsh and Gurney, 1960). A possible explanation for these manifestations is that certain iron-containing tissue enzymes, including catalase, cytochrome c, and cytochrome oxidase may be reduced in states of latent iron deficiency. Beutler (1957), Gubler, Cartwright and Wintrobe (1957) and Beutler and Blaisdell (1958) demonstrated a reduced content of cytochrome c in the organs of iron-deficient animals even when the blood haemoglobin was not greatly reduced. Using a histochemical technique, Jacobs (1961) has shown that the cytochrome-oxidase activity of buccal epithelium is reduced in some patients with frank iron-deficiency anaemia. It is of interest that one of Jacobs’s non-anaemic control subjects with absent cytochrome oxidase activity probably had latent iron deficiency (haemoglobin 13.3 g. per 100 ml.; serum iron 57 p g . per IOO ml. and total iron binding capacity 420 pg. per IOO ml.). For these reasons, an investigation has been carried out on the cytochrome-oxidase activity of buccal mucosal biopsy material from: (a) subjects with latent iron deficiency without anaemia, (b) patients with frank iron-deficiency anaemia, and (c) control subjects with normal iron stores.

Abnormal haem biosynthesis in chronic alcoholics.

Abstract. The activities of six of the enzymes of haem biosynthesis have been examined in eleven chronic alcoholics admitted to hospital for alcohol withdrawal. The mitochondrial enzymes delta‐aminolae‐vulinic acid (ALA) synthase, coproporphyrinogen oxidase and ferrochelatase were monitored in peripheral leucocytes and the cytosolic enzymes ALA dehydratase, uroporphyrinogen‐1 ‐synthase and uro‐porphyrinogen decarboxylase in peripheral erythro‐cytes. Compared with control subjects the activity of the initial and rate controlling enzyme of the pathway, ALA synthase, was increased (P < 0.01) and the activities of ALA dehydratase and uroporphyrinogen decarboxylase depressed (P < 0.01, P < 0.02 respectively) on the day after admission but all returned to normal by the tenth to twentieth days after alcohol withdrawal. This stimulation of ALA synthase and inhibition of uroporphyrinogen decarboxylase explains the mechanism by which chronic alcohol ingestion may precipitate cutaneous hepatic porphyria.

Clinical and Laboratory Studies on the Action of Desferrioxamine

Summary. Most of the published literature on the iron chelating agent desferrioxamine (DFA) relates to urinary excretion of iron following its administration. In the present study, six patients suffering from various iron storage diseases were maintained on a fixed dietary intake of iron and a basal value for faecal iron excretion was obtained. In all cases the faecal iron content rose significantly after treatment with desferrioxamine (P <0.05). The increase in faecal iron after DFA was between 30 and 50 per cent (mean 40 per cent) of the total increase in both urinary and faecal iron excretion. This finding has a relevance to the correct interpretation of tests using DFA for the assessment of body iron stores.

Lead Effects on the Heme Biosynthetic Pathway Relationship to Toxicity

The anemia of lead poisoning was first noted over 100 years ago, and since that time lead has been shown to have many dramatic effects on heme biosynthesis. In 1895, Stokvis found increased urinary porphyrins in lead-poisoned rabbits. Since then, human studies have shown similarly that lead poisoning results in increased urinary excretion of coproporphyrinZv3 and 6-aminolevulinic acid (ALA).4 There is also accumulation of protoporphyrin in erythrocyte^.^ These abnormalities are a result of lead inhibiting the activity of certain enzymes of heme biosynthesis. In particular, there is marked depression of ALA dehydratase, ferrochelatase, and coproporphyrinogen oxidase. The activity of the rate-controlling enzyme of the pathway, ALA synthase, is consequently increased. The alterations in production of porphyrins and precursors are therefore explained by these enzymic changes (FIG. The precise mechanisms by which lead acts on these enzymes of heme biosynthesis is not known. ALA dehydratase is the enzyme in the heme pathway that is most susceptible to the inhibitory effects of lead. It is likely that the lead binds to essential sulfhydryl groups, blocking the active site on the e n ~ y m e . ~ Zinc is also necessary for full activity of ALA dehydrata~e.~. The addition of zinc to erythrocytes previously exposed to lead has been shown to result in reactivation of the enzyme. It is, therefore, tempting to speculate that zinc is involved at the active site, probably in close relationship to the sulfhydryl group, and that lead and zinc may compete for the same binding site. Boudtne and co-workers studied the activity of immunologically reacting ALA dehydratase protein in erythrocytes of lead-exposed subjects. They found that the enzyme protein was increased in moderately lead-poisoned subjects, suggesting increased synthesis as a means of compensating for the inhibited activity. The mechanism by which lead inhibits the activities of coproporphyrinogen oxidase and ferrochelatase is unknown, though sulfhydryl groups are also necessary for ferrochelatase activity. The ALA synthase activity rises as a compensatory response to the diminished synthesis of free heme, a response that is enhanced by increases in the activity of heme oxygenase.

EXCESSIVE URINARY EXCRETION OF CERTAIN PORPHYRINOGENIC STEROIDS IN HUMAN ACUTE INTERMITTENT PORPHYRIA

Abstract Individual urinary 17-oxosteroid excretion was measured by gas-liquid chromatography in 6 patients with acute intermittent porphyria. There were significant elevations of aetiocholanolone glucuronide in 2 patients, of dehydroepiandrosterone glucuronide and sulphate in 2 patients, and of epiandrosterone sulphate in 3 patients. Of the 4 patients who showed these abnormalities, 2 were in relapse, and 2 had had severe attacks 8 months and 2 1 / 2 years before the investigation. The 2 patients with a normal pattern of 17-oxosteroid excretion in urine had been in remission for 15 years and 4 1 / 2 years. In the light of these results, free dehydroepiandrosterone or its sulphate were injected intraperitoneally into rats every 24 hours, and caused significant elevations of hepatic δ-aminolaevulic acid synthetase, reaching maximal levels at about 72 hours. This enzyme is the rate-limiting enzyme of haem biosynthesis and is strikingly increased in the liver in human and experimentally-induced acute porphyria. An endogenous factor has thus been found in some patients with acute porphyria which may explain certain clinical associations, such as the age of onset after puberty, and the occurrence of attacks not attributable to exogenous factors.

CARBAMAZEPINE-INDUCED NON-HEREDITARY ACUTE PORPHYRIA

Acute intermittent porphyria has hitherto been recognised as an autosomal dominant inborn error of haem metabolism characterised by a depressed activity of the enzyme uroporphyrinogen I synthase (URO.S). A case of non-hereditary acute porphyria, similar to acute intermittent porphyria, following treatment of epilepsy with carbamazepine is reported. Subsequent measurements of erythrocyte URO.S activity in a group of epileptic patients treated with various combinations of anticonvulsant drugs suggest that carbamazepine exerts a direct suppressant effect on URO.S in addition to its indirect enzyme-inducing properties.

CHESTER PORPHYRIA: BIOCHEMICAL STUDIES OF A NEW FORM OF ACUTE PORPHYRIA

A previously unrecognised form of acute porphyria has been identified in a large family in Chester, UK. Patients presented with attacks of neurovisceral dysfunction and none had experienced cutaneous photosensitivity. Biochemically, the excretion pattern of haem precursors varied between individuals; some had a pattern typical of acute intermittent porphyria, others showed that of variegate porphyria, and some had an intermediate pattern. Studies of the enzymes of haem biosynthesis in peripheral blood cells showed a dual enzyme deficiency, with reduced activity of both porphobilinogen deaminase, as seen in acute intermittent porphyria, and protoporphyrinogen oxidase, as seen in variegate porphyria. The genetic basis of this dual form of acute porphyria and its relation to the other acute porphyrias are not clear.