Total Aldehyde Dehydrogenase Activity Research Articles

A Major Intestinal Catabolite of Quercetin Glycosides, 3-Hydroxyphenylacetic Acid, Protects the Hepatocytes from the Acetaldehyde-Induced Cytotoxicity through the Enhancement of the Total Aldehyde Dehydrogenase Activity.

Aldehyde dehydrogenases (ALDHs) are the major enzyme superfamily for the aldehyde metabolism. Since the ALDH polymorphism leads to the accumulation of acetaldehyde, we considered that the enhancement of the liver ALDH activity by certain food ingredients could help prevent alcohol-induced chronic diseases. Here, we evaluated the modulating effects of 3-hydroxyphenylacetic acid (OPAC), the major metabolite of quercetin glycosides, on the ALDH activity and acetaldehyde-induced cytotoxicity in the cultured cell models. OPAC significantly enhanced the total ALDH activity not only in mouse hepatoma Hepa1c1c7 cells, but also in human hepatoma HepG2 cells. OPAC significantly increased not only the nuclear level of aryl hydrocarbon receptor (AhR), but also the AhR-dependent reporter gene expression, though not the nuclear factor erythroid-2-related factor 2 (Nrf2)-dependent one. The pretreatment of OPAC at the concentration required for the ALDH upregulation completely inhibited the acetaldehyde-induced cytotoxicity. Silencing AhR impaired the resistant effect of OPAC against acetaldehyde. These results strongly suggested that OPAC protects the cells from the acetaldehyde-induced cytotoxicity, mainly through the AhR-dependent and Nrf2-independent enhancement of the total ALDH activity. Our findings suggest that OPAC has a protective potential in hepatocyte models and could offer a new preventive possibility of quercetin glycosides for targeting alcohol-induced chronic diseases.

Is the mechanism of nitroglycerin tolerance associated with aldehyde dehydrogenase activity? A contribution to the ongoing discussion.

The aim of the study presented here was an attempt to answer the question posed in the title: Is the mechanism of nitroglycerin tolerance associated with aldehyde dehydrogenase (ALDH) activity? Here, we investigated the effect of administration (separately or jointly) of lipoic acid (LA), nitroglycerin (GTN), and disulfiram (DSF; an irreversible in vivo inhibitor of all ALDH isozymes (including ALDH2)), on the development of tolerance to GTN. We also assessed the total activity of ALDH in the rat liver homogenates. Our data revealed that not only DSF and GTN inhibited the total ALDH activity in the rat liver, but LA also proved to be an inhibitor of this enzyme. At the same time, the obtained results demonstrated that the GTN tolerance did not develop in GTN, DSF and LA jointly treated rats, but did develop in GTN and DSF jointly treated rats. This means that the ability of LA to prevent GTN tolerance is not associated with the total ALDH activity in the rat liver. In this context, the fact that animals jointly receiving GTN and DSF developed tolerance to GTN, and in animals that in addition to GTN and DSF also received LA such tolerance did not develop, is - in our opinion - a sufficient premise to conclude that the nitrate tolerance certainly is not caused by a decrease in the activity of any of the ALDH isoenzymes present in the rat liver, including ALDH2. However, many questions still await an answer, including the basic one: What is the mechanism of tolerance to nitroglycerin?

3,4-Dihydroxyphenylacetic acid is a potential aldehyde dehydrogenase inducer in murine hepatoma Hepa1c1c7 cells.

3,4-Dihydroxyphenylacetic acid (DOPAC) is one of the major colonic microflora-produced catabolites of quercetin glycosides, such as quercetin 4'-glucoside derived from onion. Here, we investigated whether DOPAC modulates the aldehyde dehydrogenase (ALDH) activity and protects the cells from the acetaldehyde-induced cytotoxicity in vitro. DOPAC was shown to enhance not only the total ALDH activity, but also the gene expression of ALDH1A1, ALDH2 and ALDH3A1 in a concentration-dependent manner. DOPAC simultaneously stimulated the nuclear translocation of NFE2-related factor 2 and aryl hydrocarbon receptor. The pretreatment of DOPAC completely protected the cells from the acetaldehyde-induced cytotoxicity. The present study suggested that DOPAC acts as a potential ALDH inducer to prevent the alcohol-induced abnormal reaction.

Benzyl isothiocyanate ameliorates acetaldehyde-induced cytotoxicity by enhancing aldehyde dehydrogenase activity in murine hepatoma Hepa1c1c7 cells

In the present study, we assessed benzyl isothiocyanate (BITC), an organosulfur compound from cruciferous vegetables, as a potential inducer of aldehyde dehydrogenase (ALDH) activity using murine hepatoma Hepa1c1c7 cells. BITC was shown to enhance not only the total ALDH activity, but also the ALDH activity of the cytosolic/microsomal and mitochondrial fraction. BITC also significantly increased the gene and protein expression of ALDH1A1, ALDH2 and ALDH3A1 in a concentration-dependent manner. Simultaneously, the gene expression of phase 2 drug-metabolizing enzymes, such as NAD(P)H: quinone oxidoreductase 1 and heme oxygenase-1, was increased by the BITC treatment. Western blot experiments revealed that BITC not only up-regulated the Nrf2 protein expression, but also stimulated the nuclear translocation of Nrf2. Furthermore, silencing Nrf2 reduced the basal and BITC-enhanced levels of the total activity and gene expression of ALDHs. The pretreatment of BITC completely mitigated the acetaldehyde-induced cytotoxicity, which was impaired by silencing Nrf2. The present study demonstrated that BITC has been identified as a potential inducer of the total ALDH activity to prevent the acetaldehyde-induced cytotoxicity.

The alterations in alcohol dehydrogenase and aldehyde dehydrogenase activities in the sera of patients with renal cell carcinoma

PurposeIn a previous study we showed that the total activity of alcohol dehydrogenase (ADH) and its isoenzyme class I was significantly higher in renal cancer (RCC) cells compared to normal kidney. The aim of this study was to compare the activities of ADH isoenzymes and aldehyde dehydrogenase (ALDH) in the sera of patients with different stages of RCC and healthy subjects. Materials and methodsSerum samples were taken from 54 patients with clear cell RCC (17 patients in stage II, 22 in stage III and 15 in stage IV) and 52 healthy patients. Class III, IV of ADH and the total ADH activity was measured by the photometric method. For the measurement of ADH class I, II and the total ALDH activity we employed the fluorometric method. ResultsThe total activity of ADH and its isoenzyme class I were significantly higher in the sera of patients with every stage of RCC compared to healthy subjects. The analysis of ALDH activity did not indicate significant differences between tested groups. ConclusionsThe increased activity of total ADH and its isoenzyme class I in the sera of patients with RCC, seems to be caused by isoenzymes being released from cancerous cells and may be useful for diagnostics of renal cancer.

The effect of inhibition of aldehyde dehydrogenase on nasal uptake of inspired acetaldehyde.

At exposure concentrations of 750 ppm or more, acetaldehyde is a rodent inhalation carcinogen that induces nasal tumors. Aldehyde dehydrogenase (ALDH) is thought to be an important detoxifying enzyme for aldehydes. Although nasal tissues express ALDH, the importance of this enzyme relative to delivered dosage rates at high-inspired concentrations is not well defined. To provide such information, uptake of inspired acetaldehyde was measured at an inspiratory flow rate that approximated the minute ventilation rate in the surgically isolated nasal cavity of F 344 rats pretreated with either saline (control) or the ALDH inhibitor, cyanamide (10 mg/kg s.c.). ALDH activities (substrate concentration 3 times the K(m)) in anterior (respiratory mucosa) and posterior (olfactory mucosa) nasal tissues averaged 160 and 210 nmol/min), respectively, in control animals (total activity 370 nmol/min), compared to 60 and 80 nmol/min, respectively, in cyanamide-pretreated rats (p < 0.05), indicating that approximately 60% inhibition was obtained. Nasal uptake was measured at 3 inspired concentrations: 10, 300, and 1500 ppm. At these concentrations, acetaldehyde uptake efficiency averaged 54, 37, and 34% in saline-pretreated rats, respectively (p < 0.05). In absolute terms, the delivered dosage rates at these exposure concentrations averaged 21, 420, and 1990 nmol/min. The concentration dependence on uptake suggests a saturable process was involved. At inspired concentrations of 300 ppm or more, the delivered dosage rates exceeded the measured specific activity for nasal ALDH of 370 nmol/min. Cyanamide pretreatment abolished the concentration dependence. Specifically, uptake efficiencies in cyanamide-pretreated rats averaged 30, 27, and 31% at inspired concentrations of 10, 300, and 1500 ppm, respectively (p > 0.05); delivered dosage rates were 12, 310, and 1780 nmol/min. Thus, cyanamide pretreatment reduced nasal-delivered dosage rates at inspired concentrations of 10, 300, and 1500 ppm, respectively by 9, 110, and 210 nmol/min, values that correspond well with the total nasal ALDH activity of 370 nmol/min. In toto, these results suggest that inspired acetaldehyde is metabolized in situ by ALDH, but at exposure concentrations of 300 ppm or greater, the delivered dosage rate may equal or exceed the capacity of this enzyme.

Influence of chronic alcohol abuse and liver disease on hepatic aldehyde dehydrogenase activity

Alcohol metabolism results in the production of acetaldehyde, a compound that is much more toxic than ethanol itself. Hepatic aldehyde dehydrogenase (ALDH) is the main enzymatic system responsible for acetaldehyde clearance from the hepatocyte. The objective of this study was to determine the modifications in ALDH activity due to chronic alcohol abuse and liver disease. ALDH activity was determined in samples of liver tissue from 69 alcoholic and 82 nonalcoholic subjects, with and without liver disease. According to the results of liver pathology examination, alcoholic patients were classified into the following groups: controls, with no liver disease (group 1), noncirrhotic liver disease patients (group 2), and cirrhotics (group 3). Nonalcoholic subjects were categorized, using the same criteria, into groups 4, 5, and 6, respectively. ALDH activity was determined spectrophotometrically at two substrate concentrations: 18 mM for total activity and 180 μM for low K m activity. High K m activity was calculated by subtracting the low K m activity value from that of total ALDH activity. Results obtained in each group were expressed as the mean ± SD of mU of g of wet weight. There were no significant differences when the total ALDH activity from the alcoholic and the nonalcoholic patients with a similar degree of liver pathology were compared: group 1, 1257 ± 587 vs. group 4, 1328.1 ± 546.2 ( p: NS); group 2, 919.1 ± 452.4 vs. group 5, 753.5 ± 412 ( p: NS); and group 3, 430.2 ± 162.4 vs. group 6, 473.2 ± 225.3 ( p: NS). On the other hand, total ALDH activity was significantly lower in cirrhotics than in controls, both among alcoholics ( p < 0.01) and among nondrinkers ( p < 0.05). The low K m activity was severely reduced in cirrhotics, both alcoholics and nonalcoholics ( p < 0.01). High K m activities in cirrhotic patients were low, compared to controls, both in alcoholics and nonalcoholics, although the difference was nonsignificant. The results of the present study suggests that chronic alcohol abuse does not depress ALDH activity. A reduction in the ALDH activity detected in patients with severe liver disease (cirrhotics) was clearly a consequence of liver damage. This reduction was due mainly to a decrease of the low K m ALDH activity, but a trend to a decrease in the high K m ALDH activity was also detected.

Aldehyde dehydrogenase (ALDH) activity in Drosophila melanogaster adults: Evidence for cytosolic localization

The subcellular localization of the aldehyde dehydrogenase activity from the ALDH (EC 1.2.1.3) enzyme has been studied in nutritionally manipulated Drosophila melanogaster adults from a wild ( LRC) and an ADH-null ( bAdh n4 ) strain. ALDH activities from ALDH or ADH (EC 1.1.1.1) enzymes were selectively inhibited by prefeeding respectively the flies sucrose solutions supplemented with either cyanamide or acetone respectively. ALDH, ADH (as a cytosolic marker) and succinate dehydrogenase (EC 1.3.9.1) (as a mitochondrial marker) activities were assayed in both the mitochondrial and cytosolic fractions isolated from flies subjected to each treatment. Total ALDH activity in the cytosolic fraction was found to be between five (ADH strain) and ten (ADH strain) times higher than that in the mitochondrial fraction. Prefeeding cyanamide resulted in a 64% (ADH strain) and a 90% (ADH strain) reduction of the cytosolic ALDH activity, whereas prefeeding acetone resulted in a 38% (ADH strain) reduction of this activity. Prefeeding both cyanamide and acetone resulted in a total inhibition of ALDH activity, which was also observed after an extended cyanamide treatment. In conclusion, our results support that, contrary to what occurs in larvae, in adults the ALDH activity from ALDH enzyme is mainly localized in the cytosolic fraction: about 85% in ADH + and 90% in ADH − strains. Although larvae and adults use different ALDH activities to detoxify acetaldehyde (from ADH and ALDH enzymes, respectively) both of them are cytosolic. Reasons for these different uses are discussed in relation to the subcellular localization of ALDH activity.

Nutritional and gonadal effects on the intra-acinar profiles of low-Km and high-Km aldehyde dehydrogenase activity in rat liver.

Total and low-Km aldehyde dehydrogenase (ALDH) activity was measured in 50-150 ng microdissected liver tissue samples of the entire sinusoidal length. High-Km ALDH activity was calculated by subtracting the low-Km ALDH values from the total ALDH activity. Enzyme activity was measured by a microchemical assay, using the oil-well technique with luminometric determination of NADH. The intra-acinar profiles of high-Km and low-Km ALDH activity could be demonstrated graphically for both male and female rats after 84 h of starvation, and after starvation and refeeding for 6 nights. In addition, the ALDH distribution patterns of juvenile, castrated, and castrated and testosterone-treated rats were determined. It could be demonstrated that starvation, and starvation followed by refeeding, lead to changes in enzyme activity which parallel the loss and regain of liver- and body-weight. The nutritional factors do not essentially alter the normal intra-acinar profiles. In juvenile rats, ALDH is lower by 30% in comparison with the controls, but sex-differences in the distribution profiles are not yet present. Castration has no effect on the amount of enzyme activity but the sex specific distribution profiles are less marked. The main effect of testosterone treatment is an elevation of low-Km ALDH in the perivenous zone. The characteristics of the intra-acinar profiles of high-Km and low-Km ALDH activity are discussed with respect to hepatic acetaldehyde oxidation and alcoholic liver damage.

Ethanol metabolizing system in drosophila. Aldehyde dehydrogenase: Functional aspects in adult and during development

1. 1. Alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) activities were determined in adult flies from several Drosophila species endowed with widely different tolerance to ethanol (ETOH). 2. 2. Plotting ALDH against ADH activities resulted in a high correlation coefficient (r = 0.966). 3. 3. This finding was confirmed in developmental studies. From early larval stage up to late adult life, DH and ALDH activities demonstrated almost parallel profiles. 4. 4. In the highly ETOH tolerant species D. melanogaster (D.m.), ADH and ALDH profiles were U-shaped; high activities in larvae, low activities in pupae and high activities in adults. 5. 5. In D. simulans (D.s.), a species less tolerant to ETOH, the profiles were L- shaped; high activities in larvae but low activities in both pupae and adults. 6. 6. Interestingly, similar activities (ADH and ALDH) were observed in the larvae of both species. 7. 7. Subcellular distribution studies of larval ALDH in both species revealed that the total ALDH activity is largely contributed by a mitochondrial high affinity enzyme. 8. 8. ALDH activity, clearly distinguishable from aldehyde oxidase (ALDOX), was visualized through analytical isoelectric focusing of the subcellular fractions. The estimated pIs for D.m. and D.s. were 4.9 and 5.2 respectively, thus different from those of ADH. 9. 9. The key biological role initially attributed to Drosophila ALDH is further supported by the present data. In addition the Drosophila developmental model opens new avenues for research on the study of genetic regulation of ADH and ALDH expression.

Effects of disulfiram on the oxidation of benzaldehyde and acetaldehyde in rat liver

The in vitro oxidation of benzaldehyde and acetaldehyde was studied in liver samples from disulfiram-treated and control rats. With 25 μM substrate, both cytosol and mitochondria appeared to make a nearly equal contribution to the oxidation of benzaldehyde, whereas ca. 90% of acetaldhyde oxydation occurred in mitochondria. When the K m values for benzaldehyde with aldehyde dehydrogenase (ALDH) were determined, two K m values (3 and 120 μM) were obtained with mitochondria, but only a single K m value (25 μM) was obtained with the cytosolic fraction. The relatively high K m (2.9 mM) found with microsomes makes it unlikely that microsomes are important in the oxidation of benzaldehyde. In intact mitochondria, with 200 μM acetaldehyde or benzaldehyde the matrix space enzyme accounted for 77 and 62%, respectively, of the total ALDH activity. When the activity was determined in a mixture containing both substrates, the activity was found not to be additive, indicating that both substrates are oxidized by the same matrix space enzyme. With subcellular fractions, from livers of disulfiram-treated and control rats, a greater degree of inhibition of ALDH was obtained when acetaldehyde was a substrate compared to that with benzaldehyde in cytosol and mitochondria. Microsomal ALDH was not inhibited by disulfiram. In liver slices from rats given disulfiram, a statistically significant inhibition was found when either 25 or 250 μM acetaldehyde was used (46 and 33%). With benzaldehyde, a significant inhibition (24%) was observed only with the lower substrate concentration. Finding that both mitochondrial fractions and slices were less inhibited at the higher substrate concentration implies that the high K m enzyme is not inhibited. It can be concluded that, in rat, disulfiram inhibiting liver ALDH not only affects oxidation of acetaldehyde, but also that of benzaldehyde.

Aldehyde dehydrogenase in drosophila: Developmental and functional aspects

Alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) activities were determined in adult flies from several Drosophila species endowed with widely different tolerance to ethanol (ETOH). Plotting ALDH against ADH activities resulted in a high correlation coefficient (r=0.966). This finding was confirmed in developmental studies. From early larval stage up to late adult life, ADH and ALDH activities demonstrated almost parallel profiles. In the highly ETOH tolerant species D. melanogaster (D.m.), ADH and ALDH profiles were U-shaped: high activities in larvae, low activities in pupae and high activities in adults. In D. simulans (D.s.), a species less tolerant to ETOH, the profiles were L-shaped: high activities in larvae but low activities in both pupae and adults. Interestingly, similar activities (ADH and ALDH) were observed in the larvae of both species. Subcellular distribution studies of larval ALDH in both species revealed that the total ALDH activity is largely contributed by a mitochondrial high affinity enzyme. ALDH activity, clearly distinguishable from aldehyde oxidase (ALDOX), was visualized through analytical isoelectric focusing of the subcellular fractions. The estimated pIs for D.m. and D.s. were 4.9 and 5.2 respectively, thus different from those of ADH. The key biological role initially attributed to Drosophila ALDH is further supported by the present data. In addition the Drosophila developmental model opens new avenues for research on the study of genetic regulation of ADH and ALDH expression.

Human placental aldehyde dehydrogenase. Subcellular distribution and properties.

Freshly obtained human term placentae were subjected to subcellular fractionation to study the localization of NAD-dependent aldehyde dehydrogenases. Optimal conditions for the cross-contamination-free subcellular fractionation were standardized as judged by the presence or the absence of appropriate marker enzymes. Two distinct isozymes, aldehyde dehydrogenase I and II, were detected in placental extracts after isoelectric focusing on polyacrylamide gels. Based on a placental wet weight, about 80% of the total aldehyde dehydrogenase activity was found in the cytosolic acid and about 10% in the mitochondrial fraction. The soluble fraction (cytosol) contained predominantly aldehyde dehydrogenase II which has a relatively high Km (9 mmol/l) for acetaldehyde and is strongly inhibited by disulfiram. The results indicate that cytosol is the main site for acetaldehyde oxidation, but the enzyme activity is too slow to prevent the placental passage of normal concentrations of blood acetaldehyde (less than 1 mumol/l) produced by maternal ethanol metabolism.

Comparative subcellular distribution of aldehyde dehydrogenase in rat, mouse and rabbit liver

The subcellular distribution of hepatic aldehyde dehydrogenase (ALDH) activity was determined in Buffalo, Fischer 344, Long-Evans, Sprague-Dawley, Wistar and Purdue/Wistar rats. These subcellular distributions were compared to the distribution of mouse and rabbit liver ALDH. For the six rat strains, at millimolar propionaldehyde concentrations, NAD-dependent ALDH activity was associated primarily with mitochondria (51%) and microsomes (30%). At millimolar acetaldehyde concentrations, NAD-dependent ALDH was primarily mitochondrial (up to 80%). Less than 1% of total NAD-dependent aldehyde dehydrogenase was found in the cytosol. The highly inbred Purdue/ Wistar line possessed significantly less acetaldehyde-NAD ALDH activity as well as less total NADP-dependent ALDH activity than the other strains. In CD-1 mouse liver, millimolar K m NAD-dependent ALDH activity was found in mitochondria (60%), microsomes (23%) and cytosol (5%). In rabbit liver, millimolar K m NAD-dependent ALDH was also distributed among mitochondria (36%), microsomes (19%) and cytosol (28%). At micromolar substrate concentrations, mitochondria possessed the majority of rat, mouse and rabbit liver ALDH activity. In all three species, NADP-dependent ALDH activity was found predominantly in the microsomal fraction (up to 65%). The cytosol possessed little NADP-dependent ALDH in any species. We conclude that there are significant species differences in the subcellular distribution of aldehyde dehydrogenase between rat, mouse and rabbit liver. In all three species, mitochondria and microsomes possessed the majority of hepatic aldehyde dehydrogenase activity. However, the cytosol of mouse and rabbit liver also made a significant contribution to total ALDH activity. For the six rat strains examined, liver cytosol possessed little or no ALDH activity.

Expression of tumor-associated aldehyde dehydrogenase during rat hepatocarcinogenesis using the resistant hepatocyte model.

The resistant hepatocyte model was used to study expression of tumor-associated aldehyde dehydrogenase (ALDH) activity during the course of rat hepatocarcinogenesis. The hepatic ALDH phenotype was determined at intervals over 280 days by histochemical analysis, total ALDH activity assays and gel electrophoresis, using propionaldehyde and NAD (P/NAD) to characterize normal liver ALDH activity or benzaldehyde and NADP (B/NADP) to determine tumor-associated ALDH activity. By total activity assays and gel electrophoresis, no significant changes in ALDH activity occurred until day 70. However, histochemical analysis clearly demonstrated changes in ALDH activity early in neoplastic development. Intense focal hepatocyte staining with P/NAD and/or B/NADP was first detectable at day 28. The number of P/NAD-positive foci increased until day 35 then declined until day 70. The number of B/NADP-positive foci also increased until day 35, but then remained relatively constant for the remainder of the experiment. GGT activity of serial sections indicated that early ALDH-positive lesions represent a small subpopulation (9%) of all GGT-positive foci. However, by day 168 a significant portion (80%) of persistent GGT-positive neoplastic nodules were also B/NADP-positive histochemically. In addition, virtually all hepatocellular carcinomas (96%) generated by this protocol possessed significantly elevated levels of tumor-associated ALDH by histochemical analysis, total ALDH activity and gel electrophoresis. These results indicate that early appearing ALDH-positive lesions may define one early subpopulation of all initiated cells that have a high probability of progressing to the ultimate neoplasm.

Subcellular distribution of human brain aldehyde dehydrogenase.

Two human brain surgery biopsies and one autopsy sample were subjected to subcellular fractionation. With either 0.12 or 6 mM-acetaldehyde as substrate, about half of the total aldehyde dehydrogenase activity was found in the mitochondrial (+ synaptosomal) fraction and less activity in the cytosolic, nuclear, and microsomal fractions. High-affinity activity was found only in the mitochondrial fraction. The enzyme in all fractions had a higher affinity for indole-3-acetaldehyde than for acetaldehyde. The kinetic data indicate the presence of several distinct aldehyde dehydrogenase isozymes that have ample capacity to oxidize both aliphatic and aromatic aldehydes in human brain.

Hepatic aldehyde dehydrogenase activity in Peromyscus genetically deficient in alcohol dehydrogenase

1. 1. Hepatic aldehyde dehydrogenase (ALDH) activity was measured in two strains of deermouse, Peromyscus maniculatus. 2. 2. There is no difference in the subcellular distribution of ALDH activity in the two strains. Animals of Adh N Adh N genotype, lacking liver alcohol dehydrogenase (ADH), had 90% of total ALDH activity in the mitochondrial fraction compared to 94% for the Adh F Adh F animals with normal ADH activity. Almost all of the remaining ALDH activity was in the hepatic cytosol with less than 1% in the microsomal fraction. 3. 3. By contrast, in mice ( Mus musculus) 43% of total hepatic ALDH activity was found in the cytosolic fraction and 55% in the mitochondrial. 4. 4. It was concluded that the subcellular distribution of hepatic ALDH activity in Peromyscus does not vary with the presence or absence of ADH and that this ALDH distribution is not similar to that reported for other rodents.

Subcellular and perisynaptic distribution of rat brain aldehyde dehydrogenase activity.

The nuclear mitochondrial and synaptosomal fractions of rat brain were each found to contain some 25-30% of the total aldehyde dehydrogenase activity. The cytoplasmic fraction had a very low total aldehyde dehydrogenase activity. There were differences in the distribution of the activity when different aldehydes were used as substrates, suggesting the presence of isoenzymes in the various subcellular compartments. When rats were treated intracisternally with 6-hydroxydopamine there was no change in brain aldehyde dehydrogenase activity, although the noradrenaline content and the activities of tyrosine hydroxylase and dopamine-beta-hydroxylase were markedly decreased. Treatment with 6-hydroxydopamine also had no significant effect on the aldehyde dehydrogenase activity in retinal homogenates. The results suggest that the aldehyde dehydrogenase activity in rat brain is predominantly outside the catecholaminergic nerve terminals.

Aldehyde dehydrogenase in 2-acetylaminofluorene-induced rat hepatomas. Characterization of antigens recognized by anti-hepatoma aldehyde dehydrogenase sera

The material in normal rat liver which cross-reacts with anti-hepatoma aldehyde dehydrogenase sera has been partially purified. The normal liver cross-reacting material is a series of proteins electrophoretically identical to the series of hepatoma-specific aldehyde dehydrogenases (aldehyde:NAD(P) + oxidoreductase, EC 1.2.1.5) induced by 2-acetylaminofluorene. The molecular weights (100 000) and the isoelectric points (6.8–7.2) of the cross-reacting material are identical to the molecular weights and pI values of the hepatoma-specific isozymes. Absorption of anti-hepatoma aldehyde dehydrogenase sera with the cross-reacting material removes an antibody population which recognizes a normal liver aldehyde dehydrogenase. This isozyme accounts for 35% of the total normal liver aldehyde dehydrogenase. A second antibody population recognizes an antigen which accounts for 10% of the total normal liver aldehyde dehydrogenase. Approx. 55% of the normal liver aldehyde dehydrogenase activity is not recognized by any antibody population. In hepatomas, 15% of the total aldehyde dehydrogenase activity is immunochemically identical to the normal liver cross-reacting material. The remaining 85% of the tumor aldehyde dehydrogenase is characterizable as hepatoma specific on the basis of these immunochemical studies.

Different forms of rat liver aldehyde dehydrogenase and their subcellular distribution

1. 1. The properties and distribution of the NAD-linked unspecific aldehyde dehydrogenase activity (aldehyde:NAD + oxidoreductase EC 1.2.1.3) has been studied in isolated cytoplasmic, mitochondrial and microsomal fractions of rat liver. The various types of aldehyde dehydrogenase were separated by ion exchange chromatography and isoelectric focusing. 2. 2. The cytoplasmic fraction contained 10–15, the mitochondrial fraction 45–50 and the microsomal fraction 35–45% of the total aldehyde dehydrogenase activity, when assayed with 6.0 mM propionaldehyde as substrate. 3. 3. The cytoplasmic fraction contained two separable unspecific aldehyde dehydrogenases, one with high K m for aldehydes (in the millimolar range) and the other with low K m for aldehydes (in the micromolar range). The latter can, however, be due to leakage from mitochondria. The high- K m enzyme fraction contained also all d-glucuronolactone dehydrogenase activity of the cytoplasmic fraction. The specific formaldehyde and betaine aldehyde dehydrogenases present in the cytoplasmic fraction could be separated from the unspecific activities. 4. 4. In the mitochondrial fraction there was one enzyme with a low K m for aldehydes and another with high K m for aldehydes, which was different from the cytoplasmic enzyme. 5. 5. The microsomal aldehyde dehydrogenase had a high K m for aldehydes and had similar properties as the mitochondrial high- K m enzyme. Both enzymes have very little activity with formaldehyde and glycolaldehyde in contrast to the other aldehyde dehydrogenases. They are apparently membrane-bound.