Exogenous Acetaldehyde Research Articles

Localization and regulation of yeast aldehyde dehydrogenase Ald4p structures

Previously, we identified yeast strains, namely SWORD, showing more robust Ald4p-GFP filament formation than the typical ALD4::GFP strains. Here, we report that Ald4p-GFP in SWORD strains favorably polymerize into gigantic structures in the cytoplasm, despite the enzyme being established as a mitochondrial resident. In addition, we have found that nocodazole, a microtubule destabilizer, has no effect on Ald4p high-order assembly, suggesting no direct association between microtubule dynamics and Ald4p structure formation. Ald4p assembly cannot be induced by sodium azide treatment, indicating that ATP is not a primary effector of Ald4p polymerization. Interestingly, addition of exogenous acetaldehyde, a substrate of the enzyme, can significantly enhance the structure formation of Ald4p, implying that structure formation may be related to enzymatic activity.

Impact of the Acetaldehyde-Mediated Condensation on the Phenolic Composition and Antioxidant Activity of Vitis vinifera L. Cv. Merlot Wine.

Acetaldehyde is a critical reactant on modifying the phenolic profile during red wine aging, suggesting that the acetaldehyde-mediated condensation can be responsible for the variation of antioxidant activity during the aging of this beverage. The present study employs exogenous acetaldehyde at six levels of treatment (7.86 ± 0.10–259.02 ± 4.95 mg/L) before the bottle aging of Merlot wines to encourage phenolic modification. Acetaldehyde and antioxidant activity of wine were evaluated at 0, 15, 30, 45, 60 and 75 days of storage, while monomeric and polymeric phenolics were analyzed at 0, 30 and 75 days of storage. The loss of acetaldehyde was fitted to a first-order reaction model, the rate constant (k) demonstrated that different chemical reaction happened in wines containing a different initial acetaldehyde. The disappearance of monomeric phenolics and the formation of polymeric phenolics induced by acetaldehyde could be divided into two phases, the antioxidant activity of wine did not alter significantly in the first phase, although most monomeric phenolics vanished, but the second phase would dramatically reduce the antioxidant activity of wine. Furthermore, a higher level of acetaldehyde could shorten the reaction time of the first phase. These results indicate that careful vinification handling aiming at controlling the acetaldehyde allows one to maintain prolonged biological activity during wine aging.

Coupled regulations of enzymatic activity and structure formation of aldehyde dehydrogenase Ald4p.

ABSTRACTPreviously, we have developed an extramitochondrial assembly system, where mitochondrial targeting signal (MTS) can be removed from a given mitochondrial enzyme, which could be used to characterize the regulatory factors involved in enzyme assembly/disassembly in vivo. Here, we demonstrate that addition of exogenous acetaldehyde can quickly induce the supramolecular assembly of MTS-deleted aldehyde dehydrogenase Ald4p in yeast cytoplasm. Also, by using PCR-based modification of the yeast genome, cytoplasmically targeted Ald4p cannot polymerize into long filaments when key functional amino acid residues are substituted, as shown by N192D, S269A, E290K and C324A mutations. This study has confirmed that extramitochondrial assembly could be a powerful external system for studying mitochondrial enzyme assembly, and its regulatory factors outside the mitochondria. In addition, we propose that mitochondrial enzyme assembly/disassembly is coupled to the regulation of a given mitochondrial enzyme activity.

Ethanol Dehydrogenase I Contributes to Growth and Sporulation Under Low Oxygen Condition via Detoxification of Acetaldehyde in Metarhizium acridum

The entomopathogenic fungi encounter hypoxic conditions in both nature and artificial culture. Alcohol dehydrogenases (ADHs) are a group of oxidoreductases that occur in many organisms. Here we demonstrate that an alcohol dehydrogenase I, MaADH1, in the locust-specific fungal pathogen, Metarhizium acridum, functions in acetaldehyde detoxification mechanism under hypoxic conditions in growth and sporulation. The MaADH1 was highly expressed in sporulation stage under hypoxic conditions. Compared with a wild-type strain, the ΔMaADH1 mutant showed inhibited growth and sporulation under hypoxic conditions, but no impairment under normal conditions. Under hypoxic conditions, ΔMaADH1 mutant produced significant decreased alcohol, but significant increased acetaldehyde compared to wild type. M. acridum was sensitive to exogenous acetaldehyde, exhibiting an inhibited growth and sporulation with acetaldehyde added in the medium. MaADH1 did not affect virulence. Our results indicated that the MaADH1 was critical to growth and sporulation under hypoxic stress by detoxification of acetaldehyde in M. acridum.

Cardioprotection induced by a brief exposure to acetaldehyde: role of aldehyde dehydrogenase 2.

We previously demonstrated that acute ethanol administration protects the heart from ischaemia/reperfusion (I/R) injury thorough activation of aldehyde dehydrogenase 2 (ALDH2). Here, we characterized the role of acetaldehyde, an intermediate product from ethanol metabolism, and its metabolizing enzyme, ALDH2, in an ex vivo model of cardiac I/R injury. We used a combination of homozygous knock-in mice (ALDH2*2), carrying the human inactivating point mutation ALDH2 (E487K), and a direct activator of ALDH2, Alda-1, to investigate the cardiac effect of acetaldehyde. The ALDH2*2 mice have impaired acetaldehyde clearance, recapitulating the human phenotype. Yet, we found a similar infarct size in wild type (WT) and ALDH2*2 mice. Similar to ethanol-induced preconditioning, pre-treatment with 50 μM acetaldehyde increased ALDH2 activity and reduced cardiac injury in hearts of WT mice without affecting cardiac acetaldehyde levels. However, acetaldehyde pre-treatment of hearts of ALDH2*2 mice resulted in a three-fold increase in cardiac acetaldehyde levels and exacerbated I/R injury. Therefore, exogenous acetaldehyde appears to have a bimodal effect in I/R, depending on the ALDH2 genotype. Further supporting an ALDH2 role in cardiac preconditioning, pharmacological ALDH2 inhibition abolished ethanol-induced cardioprotection in hearts of WT mice, whereas a selective activator, Alda-1, protected ALDH2*2 against ethanol-induced cardiotoxicity. Finally, either genetic or pharmacological inhibition of ALDH2 mitigated ischaemic preconditioning. Taken together, our findings suggest that low levels of acetaldehyde are cardioprotective whereas high levels are damaging in an ex vivo model of I/R injury and that ALDH2 is a major, but not the only, regulator of cardiac acetaldehyde levels and protection from I/R.

Calcium-dependent microneme protein discharge and in vitro egress of Eimeria tenella sporozoites

Egress is a vital step in the endogenous development of apicomplexan parasites, as it assures the parasites exit from consumed host cells and entry into fresh ones. However, little information has previously been reported on this step of Eimeria spp. In this study, we investigated in vitro egress of Eimeria tenella sporozoites triggered by acetaldehyde. We found that addition of exogenous acetaldehyde induces egress of sporozoites from primary chicken kidney cells (PCKs) and stimulate secretion of E. tenella microneme 2 protein (EtMic 2). Moreover, by using cellular calcium inhibitors, we further proved that these processes were dependent on the intracellular calcium of the parasites. Our findings provide clues to the study of interaction between eimerian parasites and their hosts.

Exogenous acetaldehyde as a tool for modulating wine color and astringency during fermentation

Wine tannins undergo modifications during fermentation and storage that can decrease their perceived astringency and increase color stability. Acetaldehyde acts as a bridging compound to form modified tannins and polymeric pigments that are less likely to form tannin–protein complexes than unmodified tannins. Red wines are often treated with oxygen in order to yield acetaldehyde, however this approach can lead to unintended consequences due to the generation of reactive oxygen species. The present study employs exogenous acetaldehyde at relatively low and high treatment concentrations during fermentation to encourage tannin modification without promoting potentially deleterious oxidation reactions. The high acetaldehyde treatment significantly increased polymeric pigments in the wine without increasing concentrations of free and sulfite-bound acetaldehyde. Protein–tannin precipitation was also significantly decreased with the addition of exogenous acetaldehyde. These results indicate a possible treatment of wines early in their production to increase color stability and lower astringency of finished wines.

Locally-generated acetaldehyde contributes to the effects of ethanol on neurosteroids and long-term potentiation in the hippocampus

As severe alcohol intoxication impairs memory function, a high concentration of ethanol (60 mM) acutely inhibits long-term potentiation (LTP), a cellular model of learning and memory, in rat hippocampal slices. Neurosteroids are involved in this LTP inhibition. We recently reported that the inhibitory effects of 60 mM ethanol are blocked by 4-methylpyrazole (4MP), an inhibitor of alcohol dehydrogenase, suggesting that acetaldehyde locally generated within the hippocampus participates in LTP inhibition. We investigated whether acetaldehyde generated by ethanol metabolism contributes to neurosteroidogenesis and LTP inhibition. Like 60 mM ethanol, we found that exogenous acetaldehyde enhanced neurosteroid immunostaining in CA1 pyramidal neurons, and that augmented neurosteroid immunostaining by high ethanol alone was blocked by 4MP but not by inhibitors of other ethanol metabolism pathways. The inhibitory effects of 60 mM ethanol on LTP were mimicked by a lower concentration of ethanol (20 mM) plus acetaldehyde (60 μM), although neither agent alone was effective at these concentrations, suggesting that 60 mM ethanol inhibits LTP via multiple actions, one of which involves acetaldehyde and the other of which requires only 20 mM ethanol. The effects of ethanol and acetaldehyde on neurosteroid staining and LTP were overcome by inhibition of neurosteroid synthesis and by blockade of N-methyl-D-aspartate receptors (NMDARs). These observations indicate that acetaldehyde generated by local ethanol metabolism within the hippocampus serves as a signal for neurosteroid synthesis in pyramidal neurons, and participates in the synaptic dysfunction associated with severe alcohol intoxication.

Mechanism of the dehydrogenase reaction of DmpFG and analysis of inter-subunit channeling efficiency and thermodynamic parameters in the overall reaction

The bifunctional, microbial enzyme DmpFG is comprised of two subunits: the aldolase, DmpG, and the dehydrogenase, DmpF. DmpFG is of interest due to its ability to channel substrates between the two spatially distinct active sites. While the aldolase is well studied, significantly less is known about the dehydrogenase. Steady-state kinetic measurements of the reverse reaction of DmpF confirmed that the dehydrogenase uses a ping-pong mechanism, with substrate inhibition by acetyl CoA indicating that NAD+/NADH and CoA/acetyl CoA bind to the same site in DmpF. The Km of DmpF for exogenous acetaldehyde as a substrate was 23.7mM, demonstrating the necessity for the channel to deliver acetaldehyde directly from the aldolase to the dehydrogenase active site. A channeling assay on the bifunctional enzyme gave an efficiency of 93% indicating that less than 10% of the toxic acetaldehyde leaks out of the channel into the bulk media, prior to reaching the dehydrogenase active site. The thermodynamic activation parameters of the reactions catalyzed by the aldolase, the dehydrogenase and the DmpFG complex were determined. The Gibb's free energy of activation for the dehydrogenase reaction was lower than that obtained for the full DmpFG reaction, in agreement with the high kcat obtained for the dehydrogenase reaction in isolation. Furthermore, although both the DmpF and DmpG reactions occur with small, favorable entropies of activation, the full DmpFG reaction occurs with a negative entropy of activation. This supports the concept of allosteric structural communication between the two enzymes to coordinate their activities.

Biomarkers of exposure and effect in human lymphoblastoid TK6 cells following [13C2]-acetaldehyde exposure.

The dose-response relationship for biomarkers of exposure (N(2)-ethylidene-dG adducts) and effect (cell survival and micronucleus formation) was determined across 4.5 orders of magnitude (50nM-2mM) using [(13)C2]-acetaldehyde exposures to human lymphoblastoid TK6 cells for 12h. There was a clear increase in exogenous N (2)-ethylidene-dG formation at exposure concentrations ≥ 1µM, whereas the endogenous adducts remained nearly constant across all exposure concentrations, with an average of 3.0 adducts/10(7) dG. Exogenous adducts were lower than endogenous adducts at concentrations ≤ 10µM and were greater than endogenous adducts at concentrations ≥ 250µM. When the endogenous and exogenous adducts were summed together, statistically significant increases in total adduct formation over the endogenous background occurred at 50µM. Cell survival and micronucleus formation were monitored across the exposure range and statistically significant decreases in cell survival and increases in micronucleus formation occurred at ≥ 1000µM. This research supports the hypothesis that endogenously produced reactive species, including acetaldehyde, are always present and constitute the majority of the observed biological effects following very low exposures to exogenous acetaldehyde. These data can replace default assumptions of linear extrapolation to very low doses of exogenous acetaldehyde for risk prediction.

Aldehyde-stress resulting from Aldh2 mutation promotes osteoporosis due to impaired osteoblastogenesis

Osteoporosis is a complex disease with various causes, such as estrogen loss, genetics, and aging. Here we show that a dominant-negative form of aldehyde dehydrogenase 2 (ALDH2) protein, ALDH2*2, which is produced by a single nucleotide polymorphism (rs671), promotes osteoporosis due to impaired osteoblastogenesis. Aldh2 plays a role in alcohol-detoxification by acetaldehyde-detoxification; however, transgenic mice expressing Aldh2*2 (Aldh2*2 Tg) exhibited severe osteoporosis with increased levels of blood acetaldehyde without alcohol consumption, indicating that Aldh2 regulates physiological bone homeostasis. Wild-type osteoblast differentiation was severely inhibited by exogenous acetaldehyde, and osteoblastic markers such as osteocalcin, runx2, and osterix expression, or phosphorylation of Smad1,5,8 induced by bone morphogenetic protein 2 (BMP2) was strongly altered by acetaldehyde. Acetaldehyde treatment also inhibits proliferation and induces apoptosis in osteoblasts. The Aldh2*2 transgene or acetaldehyde treatment induced accumulation of the lipid-oxidant 4-hydroxy-2-nonenal (4HNE) and expression of peroxisome proliferator-activated receptor gamma (PPARγ), a transcription factor that promotes adipogenesis and inhibits osteoblastogenesis. Antioxidant treatment inhibited acetaldehyde-induced proliferation-loss, apoptosis, and PPARγ expression and restored osteoblastogenesis inhibited by acetaldehyde. Treatment with a PPARγ inhibitor also restored acetaldehyde-mediated osteoblastogenesis inhibition. These results provide new insight into regulation of osteoporosis in a subset of individuals with ALDH2*2 and in alcoholic patients and suggest a novel strategy to promote bone formation in such osteopenic diseases.

Characterization of an Aldolase−Dehydrogenase Complex That Exhibits Substrate Channeling in the Polychlorinated Biphenyls Degradation Pathway

An aldolase and dehydrogenase complex from the polychlorinated biphenyl degradation pathway of the bacterium Burkholderia xenovorans LB400 was purified. The aldolase, BphI, had the highest activity with Mn(2+) as the cofactor and was able to transform 4-hydroxy-2-oxopentanoate and 4-hydroxy-2-oxohexanoate to pyruvate and acetaldehyde or propionaldehyde with similar specificity constants. Aldolase activity was competitively inhibited by the pyruvate enolate analogue, oxalate, with a K(ic) of 0.93 microM. The pH-rate profiles suggested the involvement of a pK(a) 7.7 catalytic base in the reaction mechanism. BphI activity was activated 15-fold when substrate turnover was occurring in the dehydrogenase, BphJ, which can be attributed partially to nicotinamide coenzyme binding to BphJ. BphJ had similar specificity constants for acetaldehyde or propionaldehyde and was able to utilize aliphatic aldehydes from two to five carbons in length as substrates, although K(m) values for these aldehyes were >20 mM. When 4-hydroxy-2-oxopentanoate was provided as a substrate to the BphI-BphJ complex in a coupled enzyme assay, no lag in the progress curve of BphJ was observed. When 1 mM propionaldehyde was added exogenously to a reaction mixture containing 0.1 mM 4-hydroxy-2-oxopentanoate, 95% of the CoA esters produced was acetyl CoA. Conversely, 99% of the CoA esters produced was propionyl CoA when a 10-fold molar excess of exogenous acetaldehyde was added in a reaction mixture containing 4-hydroxy-2-oxohexanoate. These results demonstrate that acetaldehyde and propionaldehyde, products of the BphI reaction, are not released in the bulk solvent but are channeled directly to the dehydrogenase.

Effect of Acetaldehyde Upon Cathepsin G and Chymase. NRAS Implications

Hypertension is commonly observed in alcoholics. Both the renin-angiotensin system (RAS) and the non-renin-angiotensin system (NRAS) have been implicated in the dynamics of blood pressure maintenance. In bilaterally nephrectomized rats, acetaldehyde has been reported to enhance the generation of the rate-limiting angiotensin I (ANG I) in the plasma, and in humans it inhibits the activity of several angiotensinases (A, B, and M) in the serum, thereby promoting a hypertensive set of reactions. We report here the results of a study on the effect of acetaldehyde upon cathepsin G and mast cell chymase. Acetaldehyde enhanced cathepsin G activity at all of the concentrations tested between 11.2 and 223.5 mM in a statistically significant manner. Since cathepsin G is one of several enzymes transforming ANG I into ANG II and is also capable of cleaving ANG II directly from angiotensinogen, we suggest that alcoholism, which will generate exogenous acetaldehyde from ingested alcohol, may be a contributory factor for an elevated cathepsin G activity and, consequently, hypertension via the NRAS. Chymase activity also is elevated in the presence of 440 mM acetaldehyde and diminished in the presence of 27 mM acetaldehyde. Since both enzymes also degrade ANG II, the degradative effects of each enzyme on ANG II may neutralize one another.

Response of wine yeast (Saccharomyces cerevisiae) aldehyde dehydrogenases to acetaldehyde stress during Icewine fermentation

We previously reported that the aldehyde dehydrogenase encoded by ALD3 but not ALD6 was responsible, in part, for the increased acetic acid found in Icewines based on the expression profile of these genes during fermentation. We have now completed the expression profile of the remaining yeast aldehyde dehydrogenase genes ALD2, ALD4 and ALD5 during these fermentations to determine their contribution to acetic acid production. The contribution of acetaldehyde stress as a signal to stimulate ALD expression during these fermentations was investigated for all ALD genes. The expression of glycerol-3-phosphate encoded by GPD2 was also followed during these fermentations to determine its role in addition to the role we already identified for GPD1 in the elevated glycerol produced during Icewine fermentation. Icewine juice (38.5 degrees Brix, 398 +/- 5 g l(-1) sugar), diluted Icewine juice (20.8 degrees Brix, 196 +/- 4 g l(-1) sugar) and the diluted juice with sugar levels equal to the original Icewine juice (36.6 degrees Brix, 395 +/- 6 g l(-1) sugar) were fermented in duplicate using the commercial wine yeast K1-V1116. Acetic acid and glycerol production increased 8.4- and 2.7-fold in the Icewine vs the diluted juice fermentation, respectively, accompanied by a fourfold transient increase in acetaldehyde in the Icewine condition during the first week. Both mitochondrial aldehyde dehydrogenases encoded by ALD4 and ALD5 were expressed, with ALD5 expression highest at the start of all fermentations and ALD4 expression increasing during the first week of each condition. ALD2, ALD4, ALD5 and GPD2 showed no differential expression between the three fermentation conditions indicating their lack of involvement in elevating acetic acid and glycerol in Icewine. When yeast fermenting the diluted fermentation was exposed to exogenous acetaldehyde, the transient spike in acetaldehyde increased the expression of ALD3 but this response alone was not sufficient to cause an increase in acetic acid. Expression of the other aldehyde dehydrogenases was unaffected by the acetaldehyde addition. The aldehyde dehydrogenases encoded by ALD2, ALD4 and ALD5 do not contribute to the elevated acetic acid production during Icewine fermentation. Expression of GPD2 was not upregulated in high sugar fermentations and does not reflect the elevated levels of glycerol found in these wines. Acetaldehyde at a concentration produced during Icewine fermentation stimulates the expression of ALD3, but has no impact on the expression of ALD2, -4, -5 and -6. Upregulation of ALD3 alone in the dilute fermentation is not sufficient to increase acetic acid in wine and requires additional responses found in cells under hyperosmotic stress. This work confirms that increased acetic acid and glycerol production during Icewine fermentation follows upregulation of ALD3 and GPD1 respectively, but upregulation of ALD3 alone is not sufficient to increase acetic acid production. Additional responses of cells under osmotic stress are required to increase acetic acid in Icewine.

Role of Acetaldehyde in the Discriminative Stimulus Effects of Ethanol

Acetaldehyde has been suggested to mediate some of the effects of ethanol. Acetaldehyde can be produced by the enzyme catalase within the brain after ethanol administration. The catalase inhibitor 3-amino-1,2,4-triazole (AT) reduces the production of acetaldehyde, and AT administration can reduce a number of ethanol-induced behavioral effects; this suggests the involvement of acetaldehyde in these behaviors. However, a role for acetaldehyde in mediating the discriminative stimulus effects of ethanol remains unclear. The contribution of acetaldehyde to the discriminative stimulus effects of ethanol was investigated by use of a two-lever drug discrimination paradigm with food reinforcement. Male Long-Evans rats were trained to discriminate water from either 1.0 or 2.0 g/kg ethanol. Stimulus substitution tests were conducted with ethanol (0-2.5 g/kg by gavage) and acetaldehyde (0-300 mg/kg intraperitoneally). A cumulative dose-response procedure was then used to investigate the effects of pretreatments with AT (0.5 and 1.0 g/kg intraperitoneally) on ethanol discrimination. Acetaldehyde up to doses that decreased response rates (300 mg/kg) did not substitute for the discriminative stimulus effects of 1.0 or 2.0 g/kg ethanol. In addition, AT pretreatment did not affect the dose-response curves for ethanol discrimination. These results show that exogenous acetaldehyde administration does not produce discriminative stimulus effects that are similar to those of ethanol. Also, pretreatment with the catalase inhibitor did not affect the dose-response curve for ethanol discrimination, and this suggests that endogenously produced acetaldehyde does not contribute to the discriminative stimulus effects of ethanol. Together these results suggest that acetaldehyde does not mediate the discriminative stimulus effects of 1.0 to 2.0 g/kg ethanol.

Effects on endogenous acetaldehyde production by disulfiram and ethanol feeding on rat pancreas

Exogenous acetaldehyde infusion can induce pancreatitis-like injury of the pancreas in some isolated pancreas models, whereas in vivo such treatment has failed to induce pancreatitis. In vivo exogenous acetaldehyde may not be effective because it is rapidly metabolized. The aim of this study was to investigate whether endogenous acetaldehyde accumulates in the pancreas after ethanol feeding when acetaldehyde metabolism is blocked by disulfiram, and whether this treatment can induce pancreatitis-like injury in the rat. The liver was studied for comparison. In part I of the experiment, adult male Wistar rats were given water (n = 24), ethanol (n = 24), disulfiram (n = 24), and ethanol plus disulfiram for 1 week (n = 24) or 3 weeks (n = 24) and for 3 weeks with (n = 6) and without (n = 6) hypovolemia. In part II of the experiment, rats were given water (n = 6), ethanol (n = 6), and high-dose disulfiram (n = 6) and ethanol plus high-dose disulfiram (n = 6). Ethanol and acetaldehyde concentrations in blood, liver, and pancreas were measured. Animal behavior was monitored, and weight changes, plasma amylase activity, water content, and histomorphology of the pancreas and liver were studied without knowing the group. No increases in plasma amylase activity and no histomorphologic changes in the pancreas were observed under light or electron microscopy in part I of the experiment. In part II, treatment with ethanol induced acetaldehyde accumulation in the liver (33.6 ± 2.6 μmol/L), but to a lesser degree in the blood (9.6 ± μmol/L) and pancreas (5.0 ± .2 μmol/L). Ethanol plus disulfiram induced marked accumulation of acetaldehyde in the liver (83.2 ± 15.9 μmol/L), blood (280.0 ± 47.4 μmol/L), and pancreas (43.6 ± 4.7 μmol/L). When tissue acetaldehyde levels reached 30 to 40 μmol/L, we found a decrease in zymogen granules along with formation of small intracytoplasmic vacuolizations in the acinar cells and accumulation of lipid droplets in the hepatocytes, whereas physiologic signs of pancreatitis (hyperamylasemia, edema) or increases in liver enzymes did not develop. High levels of acetaldehyde accumulate in the liver and pancreas with the treatment described. Although this was accompanied by lipid degeneration of the hepatocytes and some subcellular changes in the acinar cells, physiologic signs of pancreatitis did not develop. Thus acetaldehyde accumulation alone, or in combination with hypovolemia, is not responsible for the induction of acute pancreatitis.

The influence of exogenous acetaldehyde solution on the vase life of two carnation (Dianthus caryophyllils L.) cultivars in the absence or presence of exogenous ethylene

The effects of acetaldehyde concentration (0, 0.025, 0.05, 0.1, 0.2,0.3, 0.4 or 0.5%) in solution on the vase life and ethylene productionoftwo carnation (Dianthus caryophyllus L.) cultivarscontrasting in vase life (Sandrosa (long lasting) and Yellow Candy (shortlasting)) were studied. In Sandrosa, acetaldehyde solution (0.05%)increased the vase life by 3 days in the absence, or by 2 days in the presence,of exogenous ethylene; the increase in vase life was associated with a delay inthe ethylene climacteric peak. In Yellow Candy, acetaldehyde (0.05%)increased vase life by 3 days, in an ethylene free environment. In the presenceof exogenous ethylene there was no increase in vase life of Yellow Candy.Acetaldehyde failed to inhibit ethylene production in either of the cultivars.It is suggested that acetaldehyde is not involved in the inhibition of ethylenebiosynthesis or sensitivity to ethylene in these two carnation cultivars.

Evolution of Volatiles During Seed Aging

ABSTRACT Acetaldehyde, ethanol and methanol evolution was studied from soybean (Glycine max L. Merrill) and snap bean (Phaseolus vulgaris L.) seeds held at 12, 53 or 75% RH. Exogenous acetaldehyde or ethanol was applied in a gaseous phase at known concentrations to seeds in a closed container. The volatile compounds evolved were quantified by gas chromatography from the headspace or thermally derived from seed tissues. Exogenous application of acetaldehyde or ethanol resulted in enhanced ethanol or acetaldehyde evolution, respectively, at all relative humidity levels tested. The greatest conversion of acetaldehyde to ethanol was at 75% RH, while maximal conversion of ethanol to acetaldehyde occurred at 53% RH. Ethanol evolution was greater than acetaldehyde evolution from treated seeds, supporting the contention that alcohol dehydrogenase (ADH) was responsible for the conversion, and that ADH favors ethanol production. Methanol evolution was enhanced only in the headspace by application of either acetal-d...

Binding of acetaldehyde to rat liver microsomes: Enhancement after chronic alcohol consumption

Summary Rat hepatic microsomal preparations were assessed for their capacity to bind exogenous 14C-acetaldehyde and 14C-acetaldehyde formed endogenously from 14C-ethanol in the microsomal ethanol-oxidizing system (MEOS). Exogenous acetaldehyde was found to bind to rat liver microsomes. Blocking of the free amino groups and thiol groups with site specific reagents (pyridoxal 5′-phosphate and p-hydroxymercuribenzoate) reduced the binding of acetaldehyde. Acetaldehyde formed endogenously from ethanol also bound to hepatic microsomes. This was increased after chronic alcohol consumption, in association with enhanced MEOS activity. The binding of acetaldehyde produced by MEOS was significantly greater than that of an equivalent amount of exogenous acetaldehyde. Thus, acetaldehyde produced in situ may exert local toxic effects on the endoplasmic reticulum.