Coproporphyrinogen oxidase, protoporphyrinogen oxidase and ferrochelatase activities in human liver biopsies with special reference to alcoholic liver disease

The activities of coproporphyrinogen oxidase, protoporphyrinogen oxidase and ferrochelatase have been assayed in human liver biopsies using recently developed highly sensitive specific enzyme assays. The specific activities (nmol/min/mg protein) in controls were 0.010 +/- 0.003 (mean +/- S.D., n = 11), 0.18 +/- 0.07 (n = 9) and 0.062 +/- 0.022 (n = 8), respectively. The total activities (mumol/min/liver) were determined, using ultrasound to determine liver volumes, and were 2.6 +/- 0.6 (n = 5), 36.6 +/- 13.9 (n = 6) and 14.2 +/- 5.4 (n = 3), respectively. Both specific and total enzyme activities in alcoholics with fatty liver were not significantly different from normal controls. Decreased protoporphyrinogen oxidase activity (0.08 nmol/min/mg protein or 20.2 mumol/min/liver) was found in two patients with variegate porphyria. In a patient with erythrohepatic protoporphyria a reduction of the ferrochelatase activity (0.01 nmol/min/mg protein) was demonstrated.

Cytosolic aldehyde dehydrogenase (ALDH1) variants found in alcohol flushers

Although mitochondrial aldehyde dehydrogenase (ALDH2) has been thought to play a major role in acetaldehyde detoxification, and the high incidence of 'alcohol flushing' among Orientals is attributed to the inherited deficiency of ALDH2, the role of cytosolic aldehyde dehydrogenase (ALDH1) cannot be ignored. On the premise that alcohol flushing in Caucasians could be related to ALDH1 abnormalities, we examined the enzyme properties and electrophoretic mobilities of ALDH1 partially purified from red blood cells of nine unrelated alcohol flushers. One exhibited very low activity (10-20% of control level), and another exhibited moderately low activity (60%) and altered kinetic properties. The electrophoretic mobilities of these two samples were also distinguishable from the control samples. Immunological quantitation indicated that the amounts of ALDH1 protein in these two samples were not reduced in parallel with their enzyme deficiency. In the first case, the two characteristics, i.e. very low enzyme activity and alcohol flushing, were inherited by her daughter.

Ethanol-induced skeletal muscle myopathy: biochemical and histochemical measurements on type I and type II fibre-rich muscles in the young rat

Rats were pair-fed either a nutritionally complete liquid diet containing 36% of total calories as ethanol or isovolumetric amounts of the same diet in which ethanol was substituted by isocaloric glucose. Chronic ethanol feeding caused a preferential decline in the wet weight of the plantaris (predominantly Type II muscle fibres) which was accompanied by a reduction in the total DNA content. The soleus (a predominantly Type I fibre muscle) was relatively unaffected. Chronic ethanol exposure had no effect on the biochemical index of cell size (protein/DNA ratio) in either the plantaris or soleus. Quantitative histochemistry of Type II fibres in the plantaris demonstrated that ethanol caused an increase in the proportion of fibres with smaller diameters. Similar effects were observed for Type II fibres in the soleus. In contrast, ethanol exposure was associated with an increase in the relative proportion of Type I fibres with higher diameters, in both plantaris and soleus. Light microscopic examination of myopathic muscle sections demonstrated that lesions occurred without evidence of inflammation, fibrosis or other infiltration by non-muscle cells. It is concluded that chronic exposure of rats to ethanol is associated with skeletal muscle atrophy. The lesion appears to be specific for Type II fibres, irrespective of the predominant fibre type in the particular muscle.

Serum Tamm-Horsfall protein levels in childhood: relationship with age and glomerular filtration rate

Serum Tamm-Horsfall protein (THP) levels were measured in 157 infants and children, 46 cord blood samples and 75 adults using an enzyme-linked immunosorbent assay. THP levels increased significantly across the age groups, suggesting a positive relationship with age. There was a strong positive relationship between serum THP and estimated glomerular filtration rate among children with chronic renal failure.

An investigation into the effects of chronic ethanol feeding on hepatic mixed protein synthesis in immature and mature rats

1. The response of the liver to chronic ethanol feeding was investigated in sexually immature (85 g) and sexually mature (280 g) male Wistar rats. Rats received a nutritionally adequate liquid diet ad libitum, in which ethanol comprised 36% of total calories, for up to 6 weeks. Controls were pair-fed the same liquid diet in which ethanol was substituted by isocaloric glucose. 2. In immature rats, total hepatic protein, RNA and DNA contents were reduced by 12-23%. The amount of RNA, relative to protein or DNA, was also decreased by 11-12%, though the amount of protein relative to DNA was unaltered. In mature rats, no change in total hepatic protein and DNA contents were observed, though total RNA, RNA/protein ratio, RNA/DNA ratio and the amount of protein relative to DNA was reduced by 7-18%. 3. Rates of protein synthesis were measured with a flooding dose of L[4-3H]-phenylalanine without anaesthesia or surgical stress. In both immature and mature rats the fractional and absolute rates of hepatic protein synthesis and protein synthesis relative to DNA were reduced by approx 25%.

Characterisation of galactosyltransferase isoforms by ion-exchange and lectin affinity chromatography

Galactosyltransferase (GT) was isolated from human malignant ascitic fluid, and the ion-exchange and lectin affinity chromatographic behaviour of the two isoforms, GTI and GTII, investigated. The effect of neuraminidase on the binding to DEAE-Sephacel and various lectins suggests that GTII, the so-called cancer-specific isoform, is a more sialylated form of GTI.

Nutritional status in alcoholics with and without chronic skeletal muscle myopathy

There was a significant reduction in body mass index (15%) and creatinine-height index (22%) in the chronic alcoholics with atrophic quadriceps biopsies indicating significant loss of skeletal muscle protein. Various parameters of nutrition were assessed in chronic alcoholics with and without the commonly associated selective atrophy of type II skeletal muscle fibres, to determine if malnutrition is related to the muscle injury. Serum alkaline ribonuclease activity, a marker of protein nutritional status, was significantly higher in chronic alcoholics compared to controls, suggesting some degree of overall protein malnutrition. However there was no significant difference in this enzyme activity between alcoholics with and without atrophic muscle biopsies. Deficiencies of one or more of thiamine, riboflavin, pyridoxine, Vitamin B12 and folate were found in half of the chronic alcoholics. There was no preponderance of such vitamin deficiencies among those patients with atrophic muscle biopsies. It is concluded that the quadriceps type II fibre atrophy is accompanied by a generalised decrease in skeletal muscle mass and that it is not primarily related to the patient's nutritional status.

Mössbauer spectroscopy, electron microscopy and electron diffraction studies of the iron cores in various human and animal haemosiderins

Mössbauer spectroscopy has indicated significant differences in the iron-containing cores of various haemosiderins. In the present study, haemosiderin was isolated from a number of animal species including man. In addition, haemosiderin was isolated from patients with primary idiopathic haemochromatosis or with secondary (transfusional) iron-overload. The iron cores of the animal and normal human haemosiderin appear to be very similar by Mössbauer spectroscopy, and the electron diffraction data indicate a ferrihydrite structure similar to that of ferritin cores. The haemosiderin isolated from secondary iron-overload shows anomalous behaviour in its temperature-dependent Mössbauer spectra. This can be understood in terms of the microcrystalline goethite structure of the cores as indicated by electron diffraction. The haemosiderin cores obtained in the case of primary haemochromatosis have an amorphous Fe(III) oxide structure and show Mössbauer spectra characteristic of a magnetically disordered material, which only orders at very low temperatures.

Dipeptidyl peptidase IV--subcellular localization, activity and kinetics in lymphocytes from control subjects, immunodeficient patients and cord blood

Dipeptidyl peptidase IV (DPIV), a T cell enzyme, has been implicated in the regulation of lymphocyte proliferation in response to lectins and allogeneic cells. A sensitive fluorimetric assay has been established for the enzyme and used to investigate DPIV activity, kinetics and the subcellular localization in lymphocytes from control subjects, cord blood and patients with common variable hypogammaglobulinaemia (CVH) and chronic lymphatic leukaemia (CLL). Using sucrose density gradient centrifugation and organelle marker enzyme assays, in conjunction with digitonin as a selective plasma membrane perturbant and diazotized sulphanilic acid as a non-permeant enzyme inhibitor, DPIV was shown to be a plasma membrane ecto-enzyme. A significant decrease in lymphocyte DPIV activity was observed in cord blood and in patients with CVH and CLL compared to controls. Kinetic analysis showed a marked decrease in the Vmax of lymphocyte DPIV from cord blood and patients with CVH and CLL compared to controls. The apparent Km for the substrate was unaffected in cord blood and patients with CLL. However, in patients with CVH the Km was significantly reduced. Various enzyme inhibitors showed no differences between control subjects and CVH lymphocyte activities. The decreased Km for DPIV provides further evidence for a stem cell defect rather than cell immaturity in CVH.

Accurate and specific HPLC assay of coproporphyrinogen III oxidase activity in human peripheral leucocytes

An HPLC method is described for the assay of coproporphyrinogen III oxidase in human leucocytes. The optimal pH for the assay was 6.5-7.0 and the Km for coproporphyrinogen III was 0.12 +/- 0.021 mumol/l. The mean activity in 28 apparently health subjects was 0.249 (2 SD range 0.130-0.368) nmol/h per mg protein. In two patients with hereditary coproporphyria, the activities were 0.029 and 0.078 nmol/h per mg protein.

Free and total carnitine and acylcarnitine content of plasma, urine, liver and muscle of alcoholics

1. Plasma and urine free and total carnitine and acylcarnitine levels were assayed in 12 control subjects and 20 chronic alcoholics with fatty liver. Although the alcoholics had a wider range of values than the controls, there was no significant difference between the two groups. 2. Hepatic free and total carnitine and long- and short-chain acylcarnitines were assayed by a radioenzymatic method in samples from seven control subjects and seven alcoholics. No significant differences in any of the indices were noted between the patient and control groups and it was concluded that carnitine deficiency did not contribute to alcoholic fatty liver in patients without cirrhosis. 3. Skeletal muscle free and total carnitine and long- and short-chain acylcarnitines were assayed in eight alcoholics and seven control subjects. The alcoholics had significantly higher total and free carnitine levels. It is suggested that this reflects a selective enrichment of the biopsy sample with type I carnitine-rich fibres due to the type II fibre atrophy found in approximately half the patients.

The effect of chronic ethanol ingestion on protein metabolism in type-I- and type-II-fibre-rich skeletal muscles of the rat

1. The effects of chronic ethanol feeding on muscles containing a predominance of either Type I (aerobic, slow-twitch) or Type II (anaerobic, fast-twitch) fibres were studied. Male Wistar rats, weighing approx. 90 g or 280 g, were pair-fed on a nutritionally complete liquid diet containing 36% of total energy as ethanol, or isovolumetric amounts of the same diet in which ethanol was replaced by isoenergetic glucose. After 6 weeks feeding, fractional rates of protein synthesis were measured with a flooding dose of L-[4-(3)H]-phenylalanine and muscles were analysed for protein, RNA and DNA. 2. Ethanol feeding decreased muscle weight, protein, RNA and DNA contents in both small and large rats. Type-II-fibre-rich muscles showed greater changes than did Type-I-fibre-rich muscles. Changes in protein paralleled decreases in DNA. 3. The capacity for protein synthesis (RNA/protein), fractional rates of protein synthesis and absolute rates of protein synthesis were decreased by ethanol feeding in both small and large rats. The amounts of protein synthesized relative to RNA and DNA were also decreased. Changes were less marked in Type-I than in Type-II-fibre-rich muscles. Loss of protein, RNA and DNA was greater in small rats, but protein synthesis was more markedly affected in large rats. 4. It was concluded that chronic ethanol feeding adversely affects protein metabolism in skeletal muscle. Fibre composition and animal size are also important factors in determining the pattern of response.

Quantitative analysis of immunogold labelling for ferritin in liver from control and iron-overloaded rats

The distribution of ferritin antigenicity in control and iron-loaded rat hepatocytes was investigated with an immunogold-ferritin antibody technique. Antibody to horse spleen ferritin showed immunoreactivity as determined by dot blotting with immunogold/silver staining with purified rat liver ferritin but not with rat haemosiderin. The initial site of ferritin degradation was studied by analysing the density of gold labelling in the cytosol and lysosomes in combination with pre-embedding acid phosphatase cytochemistry. Immunoreactive ferritin was present in the cytosol, cytosolic clusters and lysosomes of normal hepatocytes. After iron-loading, the labelling density increased over tenfold in parenchymal cell cytosol with a smaller increase in Kupffer cells. Ferritin clusters contained substantially more immunoreactive ferritin than equivalent areas of lysosomes or cytosol. Analysis of the labelling density in hepatocyte lysosomes showed that, despite a striking increase in iron content, one-quarter of the lysosomes showed less immunolabelled ferritin than the cytosol. The existence of a wide range of ferritin labelling densities in the lysosomes with a large proportion unlabelled suggests that the ferritin protein shell is not degraded at a significant rate either in the cytosol or in clusters but only after incorporation into lysosomes.

Acute ethanol dosage reduces the synthesis of smooth muscle contractile proteins in the small intestine of the rat

The effects of an acute dose of ethanol (75 mmol/kg body weight; ip) on protein synthesis were investigated in the small intestine of the rat (n = 6). Control rats (n = 6) were injected with isovolumetric 0.15 mol/l NaCl, ip. After 2.5 h, fractional rates of protein synthesis (defined as the percentage of tissue protein renewed each day by synthesis and RNA efficiencies (defined as the amount of protein synthesised per unit RNA) were measured with a large flooding dose (0.3 Ci/mol; 150 mmol/l; 150 mumol/100 g body weight; iv) of [4(3)H]-phenylalanine. Rats were killed 10 minutes after injection of the isotope and portions of the small intestine were rapidly dissected and frozen. Tissues and plasma were processed for phenylalanine specific radioactivities to obtain fractional rates of protein synthesis or protein synthesis rates relative to RNA. Rates of protein synthesis in mixed tissue proteins fell approximately 15-25% (p ranged from less than 0.005 to greater than 0.05), in response to acute ethanol dosage. The decrease in the synthesis rates of the cytoplasmic protein fraction was similar (p less than 0.025). Proteins extracted from the smooth muscle contractile apparatus, however, showed a greater response to ethanol--that is, 40-50% inhibition in protein synthesis (p less than 0.001). It is therefore possible that the functional disturbances in the ethanol-exposed gut may be because of changes in smooth muscle protein turnover with decreased amounts of contractile apparatus.

Serum carnosinase activities in patients with alcoholic chronic skeletal muscle myopathy

1. Serum carnosinase activity was assayed in a group of alcoholic patients with and without histologically proven atrophy of type II skeletal muscle fibres, and in control subjects. No significant activity was detected in muscle biopsy samples or washed erythrocytes. 2. Serum carnosinase activity was significantly lower in chronic alcoholic patients compared with a group of age-matched controls. Alcoholics with abnormal muscle biopsies had significantly lower enzyme activities than either those patients with normal muscle biopsies or the controls. Serum enzyme activities in patients with normal muscle biopsies were not significantly different from controls. 3. Serum carnosinase activity was inversely correlated with the degree of muscle atrophy as measured by the type II fibre atrophy factor. There was a positive correlation between the enzyme activity and skeletal muscle mass as reflected by the creatinine-height index. Furthermore, the enzyme activity significantly increased, with resolution or improvement in the myopathy, in patients who abstained from alcohol. 4. Kinetic studies showed that the reduced carnosinase activity was due mainly to a decrease in the apparent Vmax. The apparent Km was significantly higher in the myopathic compared with non-myopathic alcoholics. Mixing serum from controls and patients with myopathy gave the expected values, indicating the absence of a serum enzyme inhibitory factor. Acute alcohol loading had no effect on the serum carnosinase activity. 5. The decrease in serum carnosinase activity in alcoholics was not related to the severity of their liver disease. Assays of serum carnosinase in chronic alcoholics, can thus be used as a marker of their associated myopathy.

High-performance liquid chromatography of porphyrins

Techniques for the analysis of porphyrins in the biomedical fields are reviewed. The emphasis is on high-performance liquid chromatography and its aspplications in: (1) the quantitative analysis of porphyrins in blood, urine and faeces; (2) qualitative porphyrin profiles in normal subjects and in the porphyrias; (3) assay of haem biosynthetic enzyme activities and (4) resolution of type isomers of porphyrins and porphyrinogens. Detection systems, quantitation methods, peak identification and sample preparation procedures are discussed.

Structural specificity of haemosiderin iron cores in iron-overload diseases

Haemosiderin iron cores isolated from patients with secondary haemochromatosis have a goethite-like (alpha-FeOOH) crystal structure whereas those from patients with primary haemochromatosis are amorphous Fe (III) oxide. Haemosiderin cores isolated from normal human spleen are crystalline ferrihydrite (5Fe2O3.9H2O). The disease-specific structures are significantly different from the ferrihydrite structure of associated ferritin cores. The results are important in understanding the biological processing of iron in pathological states and in the clinical treatment of iron-overload diseases.

Significance of non-esterified fatty acids in iron uptake by intestinal brush-border membrane vesicles

Iron uptake from Fe/ascorbate by mouse brush-border membrane vesicles is not greatly inhibited by prior treatment with a variety of protein-modification reagents or heat. Non-esterified fatty acid levels in mouse proximal small intestine brush-border membrane vesicles show a close positive correlation with initial Fe uptake rates. Loading of rabbit duodenal brush-border membrane vesicles with oleic acid increases Fe uptake. Depletion of mouse brush-border membrane vesicle fatty acids by incubation with bovine serum albumin reduces Fe uptake. Iron uptake by vesicles from Fe/ascorbate is enhanced in an O2-free atmosphere. Iron uptake from Fe/ascorbate and Fe3+-nitrilotriacetate (Fe3+-NTA) were closely correlated. Incorporation of oleic acid into phosphatidylcholine/cholesterol (4:1) liposomes leads to greatly increased permeability to Yb3+, Tb3+, Fe2+/Fe3+ and Co2+. Ca2+ and Mg2+ are also transported by oleic acid-containing liposomes, but at much lower rates than transition and lanthanide metal ions. Fe3+ transport by various non-esterified fatty acids was highest with unsaturated acids. The maximal transport rate by saturated fatty acids was noted with chain length C14-16. It is suggested that Fe transport can be mediated by formation of Fe3+ (fatty acid)3 complexes.

Effect of chronic ethanol feeding on the hepatic secretion of very-low-density lipoproteins

Using Triton WR-1339 to inhibit plasma metabolism of VLDL, hepatic secretion of VLDL was measured in vivo in control and alcohol-fed rats. The composition of VLDL secreted from livers of chronically alcohol-fed rats was compared with pair-fed controls. The results show that the cholesterol, esterified and nonesterified, as well as the triacylglycerol content of VLDL secreted by the alcohol-fed rats was significantly reduced; protein and phospholipid constituents of the VLDL were unaltered. The apoprotein components of the VLDL showed no apparent difference between the two groups. However, fatty-acid composition of VLDL triacylglycerol and phospholipids show a significant reduction in 20:4 and an increase in 18:2 fatty acids in the alcohol-fed rats. VLDL secretion rates by chronic alcohol-fed rats was reduced significantly compared to the control animals, and this observation has been implicated in the pathogenesis of alcoholic fatty liver.