Is porphobilinogen deaminase activity a secondary control mechanism in haem biosynthesis in humans? [proceedings].
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Biomedical subjects
Publications and source records attributed to A Goldberg.
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1. The activities of six of the enzymes of haem biosynthesis have been assayed in peripheral blood from patients with lead poisoning, acute intermittent porphyria or hereditary coproprophyria. 2. Compared with normal subjects the lead-poisoned subjects had highly significant depression of delta-aminolaevulinate dehydratase, coproporphyrinogen oxidase and ferrochelatase. 3. Lead-poisoned subjects had highly significant elevation of delta-aminolaevulinate synthase activity. 4. delta-Aminolaevulinate synthase activity was inversely related to the haemoglobin concentration. 5. Increased delta-aminolaevulinate synthase and decreased delta-aminolaevulinate dehydratase activity are also found in acute intermittent porphyria. 6. Increased delta-aminolaevulinate synthase, normal prophobilinogen deaminase and uroporphyrinogen decarboxylase and decreased coproporphyrinogen oxidase are found in both lead poisoning and hereditary coproporphyria. 7. These enzyme changes explain the recognized patterns of porphyrins and prophyrin precurosrs in blood and urine in these conditions.
1. The activities of the enzymes of haem biosynthesis were studied in 23 patients with acute intermittent porphyria. The mitochondrial enzymes delta-aminolaevulinate synthase, coproporphyrinogen oxidase and ferrochelatase were measured in leucocytes and the cytosolic enzymes delta-aminolaevulinate dehydratase, porphobilinogen deaminase and uroporphyrinogen decarboxylase in erythrocytes. 2. Leucocyte delta-aminolaevulinate synthase activity was elevated (P less than 0-001), with marked diminution of porphobilinogen deaminase activity (P less than 0-001) and reduction in the activities of delta-aminolaevulinate dehydratase (P less than 0-01) and uroporphyrinogen decarboxylase (P less than 0-005). 3. A therapeutic regimen based on intravenous laevulose infusion was studied. In four patients in acute attack and one in remission laevulose treatment was associated with a fall in delta-aminolaevulinate synthase activity, a rise in porphobilinogen deaminase and uroporphyrinogen decarboxylase activities, and a fall in urinary prophyrin precursor excretion (P less than 0-001). These studies provide a basis for the evaluation of the use of sugars in acute intermittent porphyria.
A 26-year-old woman developed photosensitivity and jaundice after starting on an oral contraceptive agent. She was found to have hereditary coproporphyria. Histological examination of two liver biopsies taken during and after the acute attack did not reveal any changes thought to be due to hereditary coproporphyria. Screening of the patient's family revealed a further six latent cases.
An analysis is presented of the obstetric histories of 50 women with acute porphyria, comprising 39 with acute intermittent porphyria, 3 with variegate porphyria and 8 with hereditary coporporphyria. Fifty-four per cent of the women with acute intermittent porphyria had an acute attack of porphyria in pregnancy and/or the puerperium. Only one maternal death was recorded. One patient with variegate prophyria and two with hereditary coproporphyria had an attack related to pregnancy. The total fetal wastage was 13 per cent. The babies born to mothers with acute intermittent porphyria, who experienced an acute attack during pregnancy, were smaller than those in which no such attack occurred (P less than 0.001). In 13 non-porphyric primigravidae there was a rise in urinary excretion of delta-aminolaevulinic acid, porphobilinogen and coproporphyrin up to the 28th week of gestation. It is probable that pregnancy has some deleterious effects in acute prophyria but the prognosis of the porphyric pregnancy is much better than the literature suggests.
The effects of aluminium, lead and zinc on ALA dehydratase were examined in vitro and in vivo. Aluminium alone added to the erythrocyte enzyme assay caused a highly significant increase in enzyme activity. A similar result was found with zinc alone. When lead and aluminium were added together, the inhibition found with lead alone was depressed in an additive manner by aluminium. Zinc and aluminium together showed an activation that was stoichiometrically additive. Studies in vivo using rats injected with aluminium and lead showed similar results for hepatic ALA dehydratase as those found in vitro.
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Hereditary coproporphyria is biochemically distinct from the other porphyrias and is characterized by excessive excretion of coproporphyrin in faeces and usually in urine. The laboratory findings in 28 patients with this disease are presented and the clinical details of eight patients who have been in attack summarised. The remaining 20 patients were latent for the disease. In all patients studied the activity of delta-aminolaevulinic acid synthase was raised and coproporphyrinogen oxidase depressed in the leucocyte. This indicates the partial enzyme block in the haem biosynthetic pathway in this disease. The activities of the other enzymes in the pathway, leucocyte ferrochelatase and erythrocyte delta-aminolaevulinic acid dehydratase, porphobilinogen deaminase and uroporphyrinogen decarboxylase showed no consistent change. On review of 111 cases, 35 per cent presented in acute attack: 80 per cent had abdominal pain, 34 per cent vomiting, 29 per cent solar sensitivity, 23 per cent neurological involvement, 23 per cent psychiatric symptoms and 20 per cent severe constipation. Only two fatalities have been published, both from respiratory failure. There was a female preponderance of cases in attack of 2-5:1 and in the latent cases of 1-5:1 suggesting hormonal provocation in the uncovering of the disease. Drugs were implicated as precipitating 54 per cent of acute attacks and in 34 per cent of cases, these were barbiturates. This study demonstrates the reduction in activity of coproporphyrinogen oxidase in the haem biosynthetic pathway and the elevation of delta-aminolaevulinic acid synthase in the peripheral blood. These features, together with the typical abnormal porphyrin excretion pattern, appear to be diagnostic of hereditary coproporphyria whether in attack, remission, or in the latent form.
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70 hypertensive patients and 70 controls matched for age and sex were investigated for a possible relationship between blood-cadmium and hypertension. No significant differences between the two groups were detected, although the blood-cadmium level was significantly higher in smokers as compared to non-smokers. These data do not support the hypothesis that cadmium is involved in the development of hypertension in man.
Blood and tap-water lead levels were examined in 135 hypertensives and 135 age and sex matched normotensives. Among male hypertensives there was a significant excess of cases with high blood-lead levels and a similar but statistically non-significant trend was found amongst female hypertensives. A positive correlation was found between blood-lead and tap-water lead. It is concluded that in the West of Scotland high blood-pressure is associated with high blood-lead levels, which might explain the high prevalence of cardiovascular disease in the area.
The frequency following response (FFR) in humans has been elicited by continuous tones as well as tone bursts. The responses were observable over a range of frequencies extending from 70 c/sec to greater than 1.5 kc/sec. The threshold for the continuous response has a mean of about 40 dB SL and is perhaps several dB lower for the burst response. The response threshold as a function of sound pressure level (SPL) increases rapidly at frequencies below 125 c/sec and above 1 kc/sec. These thresholds are particularly sharp at the lower frequencies. Narrow-band noise that just produces subjective tone masking also masks the FFR. The latency of the FFR is about 6 msec when the tone burst intensity is 30 dB over FFR threshold. Comparison with click response latencies indicates that the onset of the FFR corresponds with early waves IV and V.
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1. Kryptopyrrole (2,4-dimethyl-3-ethyl pyrrole) was shown to elevate the urinary porphyrin excretion and the hepatic content of porphyrins in the rat. The simultaneous administration of sigma-aminolaevulinic acid increased these effects. 2. Kryptopyrrole was present in the urine of patients with hereditary hepatic porphyria, in attack and in remission, but not in those with latent porphyria.
1 The activites of hepatic alcohol dehydrogenase, catalase and the reduced nicotinamide adenine dinucleotide phosphate (NADPH) dependent ethanol oxidizing system were determined in liver biopsies from nine patients with liver disease and seven control subjects with non evidence of liver disease. 2 Alcohol dehydrogenase and catalase activites were significantly lower in the patients with liver disease. 3 The activity of the NADPH dependent ethanol oxidizing system was significantly greater in the patients with liver disease, when its activity was expressed in terms of mg protein or g wet weight liver. 4 It is suggested that the greater activity of the NADPH dependent system may compensate for the low alcohol dehydrogenase activites found in patients with liver disease and maintain normal rates of ethanol metabolism.
In a double blind trial, 50 male chronic alcoholic patients were treated with either fenfluramine in a dose of 60 mg or 120 mg daily, or with identically prepared placebo tablets. Patients were interviewed on admission to the trial and then at four-weekly intervals for a period of one year and blood levels of delta-aminolaevulinic acid dehydratase (ALAD) and gamma-glutamyl transpeptidase (gammaGT) and fenfluramine were determined. The efficacy of fenfluramine at the two dose levels was compared with placebo on the basis of the number of lapses indicated by the clinical history and also by alterations in the biochemical indices. Twenty-seven patients completed the period of observation, there being 9 in each of the three groups. Those receiving 120 mg fenfluramine daily showed significantly fewer lapses than either of the other two groups (p less than 0-01) on biochemical but not on clinical criteria. Overall assessment revealed that 3 of the 9 patients receiving the high dose of fenfluramine had a good result during the period of the trial, but there were none in the 60 mg group or in those receiving placebo. More extensive trials of fenfluramine in the treatment of chronic alcoholism are indicated.