Cytochemical detection of catalase with 3,3'-diaminobenzidine. A quantitative reinvestigation of the optimal conditions

ACOX-driven peroxisomal heterogeneity and functional compartmentalization in brown adipocytes of hypothyroid rats

We previously demonstrated that hypothyroidism increases peroxisomal biogenesis in rat brown adipose tissue (BAT). We also showed heterogeneity in peroxisomal origin and their unique structural association with mitochondria and/or lipid bodies to carry out β-oxidation, contributing thus to BAT thermogenesis. Distinctive heterogeneity creates structural compartmentalization within peroxisomal population, raising the question of whether it is followed by their functional compartmentalization regarding localization/colocalization of two main acyl-CoA oxidase (ACOX) isoforms, ACOX1 and ACOX3. ACOX is the first and rate-limiting enzyme of peroxisomal β-oxidation, and, to date, their protein expression patterns in BAT have not been fully defined. Therefore, we used methimazole-induced hypothyroidism to study ACOX1 and ACOX3 protein expression and their tissue immunolocalization. Additionally, we analysed their specific peroxisomal localization and colocalization in parallel with peroxisomal structural compartmentalization in brown adipocytes. Hypothyroidism caused a linear increase in ACOX1 expression, while a temporary decrease in ACOX3 levels is only recovered to the control level at day 21. Peroxisomal ACOX1 and ACOX3 localization and colocalization patterns entirely mirrored heterogeneous peroxisomal biogenesis pathways and structural compartmentalization, e.g. associations with mitochondria and/or lipid bodies. Hence, different ACOX isoforms localization/colocalization creates distinct functional heterogeneity of peroxisomes and drives their functional compartmentalization in rat brown adipocytes.

Hypothyroidism Intensifies Both Canonic and the De Novo Pathway of Peroxisomal Biogenesis in Rat Brown Adipocytes in a Time-Dependent Manner

Despite peroxisomes being important partners of mitochondria by carrying out fatty acid oxidation in brown adipocytes, no clear evidence concerning peroxisome origin and way(s) of biogenesis exists. Herein we used methimazole-induced hypothyroidism for 7, 15, and 21 days to study peroxisomal remodeling and origin in rat brown adipocytes. We found that peroxisomes originated via both canonic, and de novo pathways. Each pathway operates in euthyroid control and over the course of hypothyroidism, in a time-dependent manner. Hypothyroidism increased the peroxisomal number by 1.8-, 3.6- and 5.8-fold on days 7, 15, and 21. Peroxisomal presence, their distribution, and their degree of maturation were heterogeneous in brown adipocytes in a Harlequin-like manner, reflecting differences in their origin. The canonic pathway, through numerous dumbbell-like and “pearls on strings” structures, supported by high levels of Pex11β and Drp1, prevailed on day 7. The de novo pathway of peroxisomal biogenesis started on day 15 and became dominant by day 21. The transition of peroxisomal biogenesis from canonic to the de novo pathway was driven by increased levels of Pex19, PMP70, Pex5S, and Pex26 and characterized by numerous tubular structures. Furthermore, specific peroxisomal origin from mitochondria, regardless of thyroid status, indicates their mutual regulation in rat brown adipocytes.

Peroxisome determination in optical microscopy: a useful tool derived by a simplification of an old ultrastructural technique

Peroxisomes are able to respond to changes in the cellular environment by adapting their number, morphology and metabolic functions. Recently interest in peroxisomes and their possible roles in physiological and pathological processes have significantly increased. In order to identify peroxisomes, several cytochemical techniques have been developed that require fairly complex procedures or are too expensive to be used for screening. In this paper we show that it is possible to label peroxisomes in several cell lines and in tissues by a simple and cheap technique based on 3,3'-diaminobenzidine (DAB) reactivity. The number of peroxisomes detected with this technique in each cell line was similar to that shown by catalase immunoreaction. The technique appears specific because it was able to detect increased number of peroxisomes after treatment with the specific PPARγ antagonist G3335. Gomori's technique for acid phosphatase activity was used to demonstrate that the DAB positive organelles were not lysosomes. The DAB technique has also been applied to transmission electron microscopy, where it labels round structures that are identified as peroxisomes on the basis of morphology, size and localization. The DAB technique has proved to be specific, simple, fast and cheap, which make it ideal to screen possible peroxisome changes in physiological and pathological conditions.

Qualitative cytological criteria for the validation of enzyme histochemical techniques

Qualitative cytological criteria are concerned with the 'precision' of a histochemical reaction and form part of the general criteria for the validation of enzyme histochemical techniques. Three major problem areas are considered: (a) the general artifacts which interfere with the 'clean' appearance of the tissue sections; (b) the exact intracellular localization of the final reaction product and its relationship to specific subcellular compartments; (c) the problem of diffusion of enzymes or reaction products, or both, from their primary subcellular sites. Each of these points is discussed and illustrated by a few examples and the conclusion is drawn that by careful consideration of various criteria the enzyme cytochemical techniques can provide 'quantitative' information comparable to biochemical measurements of enzyme activity in tissue homogenates. In the example of localization of catalase with 3,3'-diaminobenzidine it is demonstrated that biochemical enzyme assays corrrelate closely with quantitative morphometric data obtained from cytochemical preparations through an automatic image analyser system.

Expression and regulation of antioxidant enzymes in the developing limb support a function of ROS in interdigital cell death

Vertebrate limb development is a well-studied model of apoptosis; however, little is known about the intracellular molecules involved in activating the cell death machinery. We have shown that high levels of reactive oxygen species (ROS) are present in the interdigital 'necrotic' tissue of mouse autopod, and that antioxidants can reduce cell death. Here, we determined the expression pattern of several antioxidant enzymes in order to establish their role in defining the areas with high ROS levels. We found that the genes encoding the superoxide dismutases and catalase are expressed in autopod, but they are downregulated in the interdigital regions at the time ROS levels increased and cell death was first detected. The possible role of superoxide and/or peroxide in activating cell death is supported by the protective effect of a superoxide dismutase/catalase mimetic. Interestingly, we found that peroxidase activity and glutathione peroxidase-4 gene (Gpx4) expression were restricted to the non-apoptotic tissue (e.g., digits) of the developing autopod. Induction of cell death with retinoic acid caused an increase in ROS and decrease in peroxidase activity. Even more inhibition of glutathione peroxidase activity leads to cell death in the digits, suggesting that a decrease in antioxidant activity, likely due to Gpx4, caused an increase in ROS levels, thus triggering apoptosis.

A structural study of the retinal photoreceptor, plexiform and ganglion cell layers following exposure to UV-B and UV-C radiation in the albino rat

Over the last two decades, ultraviolet radiation levels (UV), reaching the Earth's surface, have been increasing at a rate of 1.5% per each 1% loss of the ozone layer. Moreover, artificial UV-sources have also proliferated and contributed to the rising UV-stress that many organisms have to face. To assess how the vertebrate retina responds to an exposure of short wavelength UV, we focused our attention on the rat retina, observing photoreceptor (containing outer and inner segments of rods and cones), inner plexiform, and ganglion cell layers by light and transmission electron microscopy using conventional and cytochemical techniques. We analyzed how cells of the layers in question responded to a 30 min exposure to UV-C and UV-B radiation with doses of 7200 and 590 J/cm(2), respectively. The results show that there are significant changes in the nuclei and cytoplasmic organelles of the exposed retinae when compared with those of the unexposed controls. The changes include an increase in heterochromatin, distension of rough endoplasmic reticulum, mitochondrial disruptions, and increases in the number of myelin bodies. The recorded morphological changes, especially those of the ganglion cells, are suggestive of apoptotic processes and show that the exposure of vertebrate retina to wavelengths ranging from 254 to 312 nm can produce alterations that are likely to impact negatively on the retina's proper functioning.

A review of morphological techniques for detection of peroxisomal (and mitochondrial) proteins and their corresponding mRNAs during ontogenesis in mice: application to the PEX5-knockout mouse with Zellweger syndrome

In the era of application of molecular biological gene-targeting technology for the generation of knockout mouse models to study human genetic diseases, the availability of highly sensitive and reliable methods for the morphological characterization of the specific phenotypes of these mice is of great importance. In the first part of this report, the role of morphological techniques for studying the biology and pathology of peroxisomes is reviewed, and the techniques established in our laboratories for the localization of peroxisomal proteins and corresponding mRNAs in fetal and newborn mice are presented and discussed in the context of the international literature. In the second part, the literature on the ontogenetic development of the peroxisomal compartment in mice, with special emphasis on liver and intestine is reviewed and compared with our own data reported recently. In addition, some recent data on the pathological alterations in the liver of the PEX5(-/-) mouse with a peroxisomal biogenesis defect are briefly discussed. Finally, the methods developed during these studies for the localization of mitochondrial proteins (respiratory chain complexes and MnSOD) are presented and their advantages and pitfalls discussed. With the help of these techniques, it is now possible to identify and distinguish unequivocally peroxisomes from mitochondria, two classes of cell organelles giving by light microscopy a punctate staining pattern in microscopical immunohistochemical preparations of paraffin-embedded mouse tissues.

Bidder's organ of Bufo ictericus: a light and electron microscopy analysis

Male toads of the Bufonidae Family have rudimentary ovaries designated Bidder's organs, and if the testes are removed this organ develops into a functional ovary, representing a morphological strategy for the reproduction of the species. The Bidder's organ of Bufo ictericus was examined using routine and histochemical techniques by light microscopy and transmission electron microscopy. Each Bidder's organ presented a typical ovarian morphology, being composed of a cortex and a medulla. Bidderian follicles in different stages of development were visualized in the cortex, where they are better developed. The germ cells exhibit a large oocyte with a round-shaped nucleus. The Bidderian follicles are supported by a loose net of reticular fibers. In the medullar region, collagen fibers were immersed in the matrix rich in blood vessels that also contained a small quantity of neutral glycoproteins rich in hexose and/or sialic acid and carboxylated polymers with a characteristic distribution of glycosaminoglycans. The oocyte and the follicular cells were separated by a narrow space containing microvilli. The oocyte exhibit a well developed smooth endoplasmic reticulum, a poorly developed Golgi apparatus, and occasional lysosomes. Concentric cisternal complexes are often visualized; however, their morphological significance remains unclear. The peroxisomes display a fine granular matrix without a crystalline core, with a weak 3,3'-diaminobenzidine-reaction. Intimate association between peroxisomes, peroxisomes and lipid inclusions was observed in the oocyte, suggesting its participation in yolk metabolism.

Temperature induced alterations in the liver of wall lizard (Hemidactylus frenatus): morphological and biochemical parameters

Wall lizards (Hemidactylus frenatus) were adapted to 20, 25, and 30 degrees C, and the liver was examined using standard transmission electron microscopy (TEM) and biochemical analysis. Peroxisomes were visualized after using the 3,3'-diaminobenzidine (DAB) technique. Catalase, uricase and protein content were determined biochemically. The hepatocytes of animals adapted to higher temperature displayed larger lipid inclusions than those of animals adapted to lower temperature. Rough endoplasmic reticulum was better developed in the animals kept at low temperature (20 and 25 degrees C) than in the animals held at 30 degrees C. Cytoplasmic crystalline structures were visualized, and better developed in the hepatocytes at 25 degrees C. Peroxisomes varied with the temperature, being more frequent in the animals kept at 20 degrees C, while the bigger ones prevailed in the animals kept at 30 degrees C. The higher catalase activity at higher temperature was correlated to an increase in staining intensity of DAB-incubated peroxisomes as visualized cytochemically in TEM. The biochemical results confirmed the cytochemical reaction observed by TEM. The hepatocytes of the animals at 30 degrees C showed a reduction in the number of peroxisomes, however, at this temperature the largest peroxisomes with a stronger reaction to DAB and a higher activity of catalase predominate. In contrast, the uricase activity showed no significant variation in relation to adaptation temperature. Overall, these data show the morphological and functional plasticity of hepatocytes to temperature adaptation of H. frenatus.

Effects of 17a-ethinylestradiol on the expression of three estrogen-responsive genes and cellular ultrastructure of liver and testes in male zebrafish

In order to monitor the influence of estrogenic compounds on the reproductive physiology of fish, molecular markers for zebrafish vitellogenin, estrogen receptor and ZP2 were developed. For this purpose, sequence information about the zebrafish estrogen receptor and vitellogenin had to be obtained. By means of RT-PCR, a sequence fragment of the zebrafish estrogen receptor alpha was cloned and sequenced. Continuous cDNAs of two zebrafish vitellogenin-like gene products (zfvg1 and zfvg3) were constructed by the help of expressed sequence tags of zebrafish and completely sequenced. The sequences of the estrogen receptor and of the vitellogenins showed significant similarities to corresponding cDNAs of other fish species. Expression of these gene products was measured following exposure to 17alpha-ethinylestradiol and compared with histological endpoints. RT-PCR was used as a semiquantitative technique to record gene expression in adult male zebrafish, which were exposed to 17alpha-ethinylestradiol in time-and dose-response experiments. As for time-dependent expression, all hepatic genes investigated were expressed at considerable amounts from 24 h after onset of exposure to 50 ng/l 17alpha-ethinylestradiol to the end of experiment (17 days). In testes, expression of the estrogen receptor- as well as ZP2-mRNA remained unchanged for the entire experiment, except for the individuals exposed for 17 days, which displayed elevated expression levels of ZP2. In the dose-response experiment, male zebrafish were exposed to 17alpha-ethinylestradiol in concentrations from 0.25-85 ng/l for 4 and 21 days. LOECs for vitellogenin as well as estrogen receptor alpha expression were found to be 2.5 ng/l already after 4 d of exposure. Extension of the exposure time to 21 days resulted in enhanced transcription of vitellogenin-mRNAs at 2.5 ng/l 17alpha-ethinylestradiol, whereas the detection limit could not be lowered. In contrast, in testes no induction of both ZP2 as well as estrogen receptor expression was detected at any concentration tested. To examine estrogen-caused alterations at the ultrastructural level, liver and testes of males exposed to 25 ng/l 17alpha-ethinylestradiol were analysed. Male livers responded with a feminisation reflected by the proliferation of rough endoplasmatic reticulum and Golgi apparatus typical of female hepatocytes during vitellogenesis. However, in testes no signs of feminisation were detectable; rather, destructive phenomena like phagocytosis of sperm cells by Sertoli cells were observed. Thus, in sexually differentiated males no reorganisation of the gonadal tissue towards an ovary could be definitely detected at any level investigated.

Contrasting effects of fish oil and safflower oil on hepatic peroxisomal and tissue lipid content

To examine the mechanism by which fish oil protects against fat-induced insulin resistance, we studied the effects of control, fish oil, and safflower oil diets on peroxisomal content, fatty acyl-CoA, diacylglycerol, and ceramide content in rat liver and muscle. We found that, in contrast to control and safflower oil-fed rats, fish oil feeding induced a 150% increase in the abundance of peroxisomal acyl-CoA oxidase and 3-ketoacyl-CoA thiolase in liver but lacked similar effects in muscle. This was paralleled by an almost twofold increase in hepatic peroxisome content (both P < 0.002 vs. control and safflower). These changes in the fish oil-fed rats were associated with a more than twofold lower hepatic triglyceride/diacylglycerol, as well as intramuscular triglyceride/fatty acyl-CoA, content. In conclusion, these data strongly support the hypothesis that n-3 fatty acids protect against fat-induced insulin resistance by serving as peroxisome proliferator-activated receptor-alpha ligands and thereby induce hepatic, but not intramuscular, peroxisome proliferation. In turn, an increased hepatic beta-oxidative capacity results in lower hepatic triglyceride/diacylglycerol and intramyocellular triglyceride/fatty acyl-CoA content.

The role of 15-lipoxygenase in disruption of the peroxisomal membrane and in programmed degradation of peroxisomes in normal rat liver

Our earlier electron microscopic observations revealed that prolonged exposure of glutaraldehyde-fixed rat liver sections to buffer solutions induced focal membrane disruptions of peroxisomes with catalase diffusion as shown cytochemically. Recently, it was suggested that 15-lipoxygenase (15-LOX) might be involved in natural degradation of membrane-bound organelles in reticulocytes by integrating into and permeabilizing the organelle membranes, leading to the release of matrix proteins. We have now investigated the localization of 15-LOX and its role in degradation of peroxisomal membranes in rat liver. Aldehyde-fixed liver slices were incubated in a medium that conserved the 15-LOX activity, consisting of 50 mM HEPES-KOH buffer (pH 7.4), 5 mM mercaptoethanol, 1 mM MgCl(2), 15 mM NaN(3), and 0.2 M sucrose, in presence or absence of 0.5-0.05 mM propyl gallate or esculetin, two inhibitors of 15-LOX. The exposure of aldehyde-fixed liver sections to this medium induced focal disruptions of peroxisome membranes and catalase diffusion around some but not all peroxisomes. This was significantly reduced by both 15-LOX inhibitors, propyl gallate and esculetin, with the latter being more effective. Double immunofluorescent staining for 15-LOX and catalase revealed that 15-LOX was co-localized with catalase in some but not all peroxisomes in rat hepatocytes. By postembedding immunoelectron microscopy, gold labeling was localized on membranes of some peroxisomes. These observations suggest that 15-LOX is involved in degradation of peroxisomal membranes and might have a physiological role in programmed degradation and turnover of peroxisomes in hepatocytes. (J Histochem Cytochem 49:613-621, 2001)

Electron microscopical investigation on aldrin-induced hepatocyte pathology in Rana catesbeiana, with special emphasis on peroxisomes

We examined the effect of aldrin on hepatocyte ultrastructure in liver of Rana catesbeiana. The frogs were experimentally exposed to chemical substance and liver fragments processed for routine transmission electron microscopy. Hepatic peroxisomes were visualized after incubation with alkaline 3,3'-diaminobezidine (DAB) method. Ultrastructural analysis revealed progressive hepatocyte changes induced by this drug. After 2-weeks, in the hepatocytes the nuclear envelop and the cisternae of both smooth and rough endoplasmic reticulum (SER und RER, respectively) were unusually enlarged. Reduction of glycogen granules associated with an increased frequency of lysosomes was observed. Normal appearing peroxisomes were present in clusters. Lipid droplets were also visualuzed. After 4-weeks, there was a new increase of glcogen associated with a great number of mitochondria and peroxisomes. Moreover, SER und RER were still dilated. Intracellular lipid inclusions became more abundant. These results suggest that the aldrin 250 induces ultrastructural changes in the hepatocyte of Rana catesbeiana.

Current cytochemical techniques for the investigation of peroxisomes. A review

The past decade has witnessed unprecedented progress in elucidation of the complex problems of the biogenesis of peroxisomes and related human disorders, with further deepening of our understanding of the metabolic role of this ubiquitous cell organelle. There have been many recent reviews on biochemical and molecular biological aspects of peroxisomes, with the morphology and cytochemistry receiving little attention. This review focuses on the state-of-the-art cytochemical techniques available for investigation of peroxisomes. After a brief introduction into the use of the 3,3'-diaminobenzidine method for localization of catalase, which is still most commonly used for identification of peroxisomes, the cerium technique for detection of peroxisomal oxidases is discussed. The influence of the buffer used in the incubation medium on the ultrastructural pattern obtained in rat liver peroxisomes in conjunction with the localization of urate oxidase in their crystalline cores is discussed, particularly since Tris-maleate buffer inhibits the enzyme activity. In immunocytochemistry, quantitation of immunogold labeling by automatic image analysis enables quantitative assessment of alterations of proteins in the matrix of peroxisomes. This provides a highly sensitive approach for analysis of peroxisomal responses to metabolic alterations or to xenobiotics. The recent evidence suggesting the involvement of ER in the biogenesis of "preperoxisomes" is mentioned and the potential role of preembedding immunocytochemistry for identification of ER-derived early peroxisomes is emphasized. The use of GFP expressed with a peroxisomal targeting signal for the investigation of peroxisomes in living cells is briefly discussed. Finally, the application of in situ hybridization for detection of peroxisomal mRNAs is reviewed, with emphasis on a recent protocol using perfusion-fixation, paraffin embedding, and digoxigenin-labeled cRNA probes, which provides a highly sensitive method for detection of both high- and low-abundance mRNAs encoding peroxisomal proteins. (J Histochem Cytochem 47:1219-1232, 1999)

In situ heterogeneity of peroxisomal oxidase activities: an update

Oxidases are a widespread group of enzymes. They are present in numerous organisms and organs and in various tissues, cells, and subcellular compartments, such as mitochondria. An important source of oxidases, which is investigated and discussed in this study, are the (micro)peroxisomes. Oxidases share the ability to reduce molecular oxygen during oxidation of their substrate, yielding an oxidized product and hydrogen peroxide. Besides the hydrogen peroxide-catabolizing enzyme catalase, peroxisomes contain one or more hydrogen peroxide-generating oxidases, which participate in different metabolic pathways. During the last four decades, various methods have been developed and elaborated for the histochemical localization of the activities of these oxidases. These methods are based either on the reduction of soluble electron acceptors by oxidase activity or on the capture of hydrogen peroxide. Both methods yield a coloured and/or electron dense precipitate. The most reliable technique in peroxisomal oxidase histochemistry is the cerium salt capture method. This method is based on the direct capture of hydrogen peroxide by cerium ions to form a fine crystalline, insoluble, electron dense reaction product, cerium perhydroxide, which can be visualized for light microscopy with diaminobenzidine. With the use of this technique, it became clear that oxidase activities not only vary between different organisms, organs, and tissues, but that heterogeneity also exists between different cells and within cells, i.e. between individual peroxisomes. A literature review, and recent studies performed in our laboratory, show that peroxisomes are highly differentiated organelles with respect to the presence of active enzymes. This study gives an overview of the in situ distribution and heterogeneity of peroxisomal enzyme activities as detected by histochemical assays of the activities of catalase, and the peroxisomal oxidases D-amino acid oxidase, L-alpha-hydroxy acid oxidase, polyamine oxidase and uric acid oxidase.

Immunocytochemical localization of L-alpha-hydroxyacid oxidase in dense bar of dumb-bell-shaped peroxisomes of monkey kidney

Localization of the B of L-alpha hydroxyacid oxidase (HOX-B) in monkey kidney peroxisomes was investigated by immunoelectron microscopic techniques. Kidneys of Japanese monkeys, Macaca fuscata, were fixed with 4% paraformaldehyde + 0.25% glutaraldehyde and embedded in LR White resin. Thin sections were stained for HOX-B and catalase by the immunogold technique. HOX-B was localized in the marginal plates of normal peroxisomes and the dense bar of dumb-bell-shaped peroxisomes. Catalase was detected in the matrix of normal peroxisomes and in the terminal dilatations of dumb-bell-shaped peroxisomes. There were no gold particles indicating presence of catalase associated with the marginal plates or with the dense bars. Immunoblot analysis of monkey kidney homogenate showed that HOX-B has a molecular mass of 42 kDa that was slightly larger than that of rat kidney HOX-B (39 kDa). The results show that the dense bar of dumb-bell-shaped peroxisomes in monkey kidney is composed of at least HOX-B and is a variation of the marginal plates.

ATP-dependent degradation of a mutant serine: pyruvate/alanine:glyoxylate aminotransferase in a primary hyperoxaluria type 1 case

Primary hyperoxaluria type 1 (PH 1), an inborn error of glyoxylate metabolism characterized by excessive synthesis of oxalate and glycolate, is caused by a defect in serine:pyruvate/alanine:glyoxylate aminotransferase (SPT/AGT). This enzyme is peroxisomal in human liver. Recently, we cloned SPT/AGT-cDNA from a PH 1 case, and demonstrated a point mutation of T to C in the coding region of the SPT/AGT gene encoding a Ser to Pro substitution at residue 205 (Nishiyama, K., T. Funai, R. Katafuchi, F. Hattori, K. Onoyama, and A. Ichiyama. 1991. Biochem. Biophys. Res. Commun. 176:1093-1099). In the liver of this patient, SPT/AGT was very low with respect to not only activity but also protein detectable on Western blot and immunoprecipitation analyses. Immunocytochemically detectable SPT/AGT labeling was also low, although it was detected predominantly in peroxisomes. On the other hand, the level of translatable SPT/AGT-mRNA was higher than normal, indicating that SPT/AGT had been synthesized in the patient's liver at least as effectively as in normal liver. Rapid degradation of the mutant SPT/AGT was then demonstrated in transfected COS cells and transformed Escherichia coli, accounting for the low level of immunodetectable mutant SPT/AGT in the patient's liver. The mutant SPT/AGT was also degraded much faster than normal in an in vitro system with a rabbit reticulocyte extract, and the degradation in vitro was ATP dependent. These results indicate that a single amino acid substitution in SPT/AGT found in the PH1 case leads to a reduced half-life of this protein. It appears that the mutant SPT/AGT is recognized in cells as an abnormal protein to be eliminated by degradation.

Crystalloid smooth endoplasmic reticulum in the quail uropygial gland

The occurrence, localization and organization of crystalloid smooth endoplasmic reticulum (SER) membrane aggregates in the male quail uropygial gland was investigated by electron microscopy. The lattice-like structures exhibiting a hexagonal honeycomb pattern are regularly found in the perinuclear region of the fully developed intermediate cell (type II) which is most effective in lipid biosynthesis and constitutes the middle layers of the stratified glandular epithelium undergoing sebaceous transformation. The crystalloids frequently exhibit a rectangular shape and tend to cluster, the latter exceeding 5 microns in length. They are composed of sets of highly ordered and densely packed tubular SER profiles. Diaminobenzidine (DAB) stained peroxisomes exhibit a close spatial relationship to the borders of crystalloids, but the organelles do not participate in the formation of these grid-like structures. The functional significance of the conformational change of the SER organization is not known. Local accumulation of specific lipogenic enzymes within this functional SER domain is discussed.

Proliferation of myocardial peroxisomes in experimental rat diabetes: a biochemical and immunocytochemical study

Myocardial peroxisomes were investigated in normal and diabetic rats. Catalase and acyl-CoA oxidase activities were increased in the diabetic rat heart and immunoblot analysis showed that both enzyme proteins were markedly enhanced in diabetic heart homogenates. After immunoenzyme staining, catalase and acyl-CoA oxidase were localized in fine granules in the myocardium, which were increased in number in diabetic rats. The numerical density of the granules stained for catalase was increased 1.7 times and that for acyl-CoA oxidase 1.8 times, compared with controls. Protein A-gold labeling for catalase and acyl-CoA oxidase was present in myocardial peroxisomes. The labeling density for both enzymes was increased in diabetic rats by 1.6 times for catalase and 1.5 times for acyl-CoA oxidase, compared with controls. The results indicate that myocardial peroxisomes are increased in the diabetic rat and that this proliferation is accompanied by an increase in catalase and acyl-CoA oxidase activities.

Ultrastructural alterations in liver of medaka (Oryzias latipes) exposed to diethylnitrosamine

Liver cytotoxic alterations of adult medaka (Oryzias latipes) following short-term bath exposure (48 hr) to 500 mg/L diethylnitrosamine (DEN) were studied (days 3-21) by electron microscopy and cytochemistry. Control medaka displayed hepatic sexual dimorphism as described for other sexually active fish. Following DEN exposure, decreased glycogen stores with loss of cellular compartmentation obscured sexual dimorphism. A spectrum of organelle alterations, previously not reported in livers of fish, was seen. Early changes in hepatocytes included: nuclear lipid inclusions, nucleolar changes, decreased amounts of granular endoplasmic reticulum (GER), increased fractionation and steatosis of GER, proliferation of smooth ER and lysosomes, reduction in number and content of particulate lipoproteins and vitellogenin in Golgi vesicles, and reduction in number and staining intensity of peroxisomes. At day 14 and/or 21, partial to complete reversal of the above alterations indicated hepatic recovery, and fewer necrotic cells were seen at day 21 versus day 14. Lesions that did not resolve during this study were altered mitochondria and areas of spongiosis hepatis that developed at day 8 and continued to increase throughout the study. Infiltration of lymphocytes, granulocytes, and large numbers of macrophages were late changes. The description, timing, and duration of lesions are of value for consideration as biomarkers of exposure and effect in aquatic toxicology.

Peroxisomes in guinea pig liver: their peculiar morphological features may reflect certain aspects of lipoprotein metabolism in this species

We have studied the ultrastructural characteristics and the distribution of peroxisomes in guinea pig liver using electron-microscopic cytochemistry for catalase and morphometry. By light microscopy, peroxisomes appear as dark 0.2-0.5 microns granules in the cytoplasm of liver parenchymal cells, often forming large clusters that measure up to 5 microns across. Rows of single peroxisomes or their aggregates line the sinusoidal surface of hepatocytes. Electron microscopy reveals that clusters of up to 25 individual peroxisomes are usually located in the subsinusoidal region of parenchymal cells. The mean diameter and the volume density of peroxisomes are larger in pericentral than in periportal regions of the liver lobule. Whereas large amounts of lipoprotein particles with a mean diameter of 160 nm (chylomicrons) are present in the Disse space, the cytoplasm of parenchymal cells contains multivesicular bodies and abundant lipid droplets. In addition, the Golgi complexes show distended lipoprotein-filled vesicles suggesting active biosynthesis of lipoproteins. We propose that the unique features of peroxisomes in guinea pig liver, such as cluster formation and alignment along the sinusoidal surface, may be related to the high levels of lipoproteins in the portal circulation and their hepatic catabolism in this species.

Species-specific reaction of liver ultrastructure in Zebrafish (Brachydanio rerio) and trout (Salmo gairdneri) after prolonged exposure to 4-chloroaniline

The morphological alterations of hepatocytes of female zebrafish, Brachydanio rerio, and fingerling rainbow trout, Salmo gairdneri, following prolonged exposure to 0.04, 0.2 and 1 mg/L of 4-chloroaniline were investigated by means of light and electron microscopy. Changes in peroxisomes were visualized by cytochemical demonstration of catalase activity after incubation in the alkaline diaminobenzidine medium. The amount of storage products was illustrated by the silver impregnation technique. In a dose-dependent manner, the reaction of female zebrafish liver is characterized by a disturbance of hepatocytic compartmentation, progressive fenestration and fractionation of the rough endoplasmic reticulum (RER), a decrease in the number of peroxisomes and catalase activity, stratified inclusions in mitochondria, and an augmentation of lysosomes and myelinated bodies. Trout hepatocytes display nuclear inclusions, fractionation and vesiculation of the RER, and an increase in mitochondria, but a decrease of peroxisomes and catalase activity. Whereas glycogen stores are exhausted at 1 mg/L 4-chloroaniline, lipid deposits are amplified. An elevated rate of hepatocytic mitosis as well as the occurrence of glycogen-condensing cells probably derived from hepatocytes indicate the induction of proliferative processes in trout liver. Evaluation and comparison of results with earlier reports suggest that despite the unspecificity of some alterations the combination of pathological symptoms yields a syndrome specific of the species and the substance studied. As a consequence, histological and cytological investigations are recommended as a routine supplement in an integrated test schedule for the assessment of sublethal effects of pollutants in the aquatic environment.

A freeze-etch study of angular marginal-plate-containing peroxisomes in the proximal tubules of bovine kidney

The ultrastructure of peroxisomes in the proximal nephron tubules of bovine kidney cortex was studied using ultrathin-sectioning, diaminobenzidine cytochemistry for the visualization of catalase, and by freeze-fracture. Peroxisomes in this nephron segment are up to 1.5 microns in diameter and exhibit a peculiar angular shape, which is probably related to the occurrence of multiple straight plate-like inclusions (marginal plates) in the matrix of peroxisomes; they lie directly underneath the peroxisomal membranes. The peroxisomal membrane in such regions follows the outline of the marginal plate. The peculiar shape of peroxisomes allows their unequivocal identification in freeze-fracture preparations. Peroxisomal membranes are recognized by their flat, often rectangular appearance. Intramembrane particles are much more numerous on P-fracture faces than on E-fracture faces. A crystalline lattice-structure with a periodicity of approximately 10 nm can be observed on the flat rectangular areas of E-fracture faces. This lattice structure is intensified after prolonged freeze-etching. Intramembranous particles seem to be superimposed over this pattern. The crystalline pattern on the E-fracture faces of peroxisomal membranes is probably not a membrane structure but it reveals the structure of the membrane-associated marginal plates. A cast of the marginal-plate surface may be generated by a collapse of the peroxisomal membrane half onto the immediately underlying matrix inclusion.

Cytochrome oxidase histochemistry in the rat hippocampus. A quantitative methodological study

The diaminobenzidine (DAB) method was adapted for the microphotometric determination of cytochrome c oxidase (cyt ox) in the rat hippocampus. The qualitative and quantitative investigations at the light microscopic level showed that acetone and cytochrome c pretreatment of cryostat sections resulted in a significant increase of demonstrable cyt ox activities. The final incubation medium consisted of 7.5 mM DAB, 2% polyvinylalcohol (PVA) and 6% dimethyl sulfoxide in 0.1 M Hepes buffer; final pH 7.5. PVA was used to keep DAB and artificially oxidized DAB in solution. In the kinetic and endpoint measurements a linear response of the reaction with highest slope was observed only in the initial 5-6 min of reaction. Thereafter the slope decreased. Ultracytochemical demonstrations, which were performed as a topochemical control, showed reaction product only in mitochondria (cristae and intermembranous space). In contrast to vibratome sections all mitochondria reacted positively in cryostat sections of aldehyde-fixed hippocampi. The enhancement of reaction after acetone pretreatment of cryostat sections (light microscopic level) and after a freezing step in ultracytochemistry is discussed in connection with diffusion problems of DAB through mitochondrial membranes.

Uptake and axonal transport of horseradish peroxidase isoenzymes by different neuronal types

The uptake and transport of basic and acidic horseradish peroxidase isoenzymes was compared in the neuromuscular, visual and olfactory systems of Xenopus larvae and postmetamorphic frogs. The concentration (w/v) of the two preparations was corrected to compensate for their difference in enzymatic activity (unit/w), which was seven-fold higher in basic horseradish peroxidase. Uptake and transport of horseradish peroxidase isoenzymes could be demonstrated with 7% basic horseradish peroxidase, but not with equal amounts of 49% acidic horseradish peroxidase in all systems investigated: retrograde transport from terminals of retinal ganglion cells, isthmotectal neurons and spinal motoneurons, as well as anterograde transganglionic transport along olfactory neurons. A very weak labelling of the same neuronal pathways by acidic horseradish peroxidase was obtained only after increasing the amount injected by approximately two-fold. Basic horseradish peroxidase isoenzymes were also preferentially taken up and transported retrogradely by broken axons of the optic nerve. When tested, similar results were obtained in both larvae and frogs suggesting that preferential uptake and transport of basic horseradish peroxidase is a general feature of all neurons and of all developmental stages. Electron microscopical analysis of the outer layers of the optic tectum revealed that, in the same experimental conditions producing no retrotrade labelling of optic axons, acidic horseradish peroxidase was rarely found to enter nerve terminals. It appears that interactions between horseradish peroxidase and neuronal membranes occur during uptake and transport and that molecular charge plays an important role, beyond non-specific fluid-phase endocytosis. We suggest that differences between horseradish peroxidase isoenzymes as neuronal tracers reflect a process of adsorptive endocytosis related to general characteristics of neuronal membranes (regardless of age) and not to specific receptor-mediated interactions characteristic of neuronal specificity.

Immunocytochemical localization of serine: pyruvate aminotransferase in peroxisomes of the human liver parenchymal cells

The localization of serine:pyruvate aminotransferase (SPT) in human liver was investigated by indirect immunoenzyme and protein A-gold techniques. By light microscopy, diaminobenzidine reaction product was present in cytoplasmic granules of the parenchymal cells. By electron microscopy, gold particles indicating the antigenic sites for SPT were exclusively confined to peroxisomes but not to mitochondria. By double labeling technique, both peroxisomal marker enzyme, catalase and SPT were detected in the same peroxisomes. Quantitative analysis of the labeling density showed that SPT is contained only in peroxisomes. The results indicate that in human liver most of SPT is contained in the peroxisomes.

Ultrastructure of hepatocytes in golden ide (Leuciscus idus melanotus L.; Cyprinidae: Teleostei) during thermal adaptation

The morphological alterations of hepatocytes of golden ide, Leuciscus idus melanotus, following adaptation to low and high temperatures (14 and 28 degrees C) were investigated by means of light and electron microscopy. The temperature-dependent behaviour of peroxisomes was visualized cytochemically with the alkaline diaminobenzidine medium; the morphological studies were supplemented by the biochemical determination of catalase activity. Cold adaptation of ide hepatocytes is manifested by proliferation and stacking of endoplasmic reticulum, an enhanced secretory activity of Golgi fields and a higher number of peroxisomes as compared with the warm-adapted animals. The latter organelles are characterized by a marked heterogeneity in size, shape and catalase activity, and by a more intimate association with mitochondria and endoplasmic reticulum. The occurrence of small peroxisomal profiles is restricted to lower temperature. Catalase activity can be shown both cytochemically and biochemically to increase during cold adaptation. Whereas the number of mitochondria seems to be unaffected by thermal adaptation, stacking of mitochondria as well as the formation of intramitochondrial membrane piles indicate cold-adaptive processes. A feature typical of warm-adaptation is the formation of membrane-glycogen complexes, which may represent the morphological expression of enhanced carbohydrate metabolism documented in a decreased storage of glycogen at 28 degrees C. At 28 degrees C lipid is the predominant storage product. These findings indicate that fish liver is well-suited to serve as a model for the analysis of the interaction of environmental temperature conditions and hepatic morphology.

Quantitative immunocytochemical studies on differential induction of serine:pyruvate aminotransferase in mitochondria and peroxisomes of rat liver cells by administration of glucagon or di-(2-ethylhexyl)phthalate

Differential induction of serine: pyruvate amino-transferase (SPT) in rat liver parenchymal cells by administration of glucagon or di-(2-ethylhexyl)phthalate (DEHP) was studied using post-embedding immunocytochemical techniques and morphometric methods. Two groups of rats were fasted for 5 days and daily received peritoneal injection of glucagon (300 micrograms/100 g) or physiological saline. Another two groups of rats were fed on laboratory chow with or without 2% DEHP for 2 weeks. Livers were perfusion-fixed, cut into tissue sections (50-100 micron), and processed to cytochemistry for catalase, immunocytochemistry for SPT, and conventional procedures for electron microscopy. The morphometric analysis showed that glucagon injection has negligible effect on the volume and numerical density and mean diameter of peroxisomes, whereas volume density of mitochondria was decreased by 25%. By DEHP administration peroxisomes were about 3-fold increased in the volume and numerical density. Mitochondria was increased about 40% in the numerical density, but unchanged in the volume density. Light and electron microscopic immunocytochemistry demonstrated that glucagon injection exclusively enhanced mitochondrial SPT, whereas DEHP administration exclusively induced in peroxisomal SPT. Quantitative analysis showed that by the glucagon injection, the labeling density of mitochondria was increased about 4-fold, but that of peroxisomes was 1.6 times as much as control, while by DEHP administration, the labeling density of peroxisomes was enhanced about 3-fold but that of mitochondria was decreased by 13%. The results clearly indicate that glucagon induces mitochondrial SPT, whereas peroxisome proliferator, DEHP induces peroxisomal SPT.

Serial section analysis of mouse hepatic peroxisomes

The ultrastructure and organization of mouse hepatic peroxisomes were investigated using serial thin sections and the alkaline diaminobenzidine technique for visualization of the peroxidatic activity of catalase. Mouse periportal hepatocytes exhibit three classes of peroxisomes which display morphological and cytochemical heterogeneity: 1) large, circular to ovoid organelles containing a crystalline nucleoid, 2) small, circular to elongate, anucleoid particles, and 3) tail-like extensions which are devoid of both catalase activity (only traces of reaction deposits) and a crystalline core. Serial section analysis reveals that these profiles correspond to three diverse interconnecting peroxisomal segments which constitute a highly complex organelle. In particular, the large nucleoid-containing peroxisomal segment exhibits an intimate relationship to the endoplasmic reticulum. However, direct membrane continuities between the two compartments are never observed. With respect to the complex structure of the organelle the following conclusions can be drawn concerning biochemical studies on liver peroxisomes: 1) During homogenization and subcellular fractionation procedures, fragmentation of peroxisomes into particles of different size classes should be expected. 2) These peroxisomal fragments are inhomogeneous with respect to their matrix contents and possess at least one rupture site on their membrane surface. 3) Soluble matrix and, to a lesser degree, membrane components of peroxisomes contribute to the soluble fraction. 4) Crude microsomal fractions are regularly contaminated by peroxisomal membrane fragments.

Marginal plates in hepatic peroxisomes of Ichthyophis glutinosus (Amphibia: Gymnophiona). A cytochemical study

The ultrastructure of hepatic peroxisomes was investigated in Ichthyophis glutinosus (Amphibia: Gymnophiona), employing perfusion fixation and the diaminobenzidine (DAB) technique for the visualization of catalase. The majority of peroxisomes is circular or rod-shaped, although elongated particles occasionally occur. They contain a finely granular matrix, lightly stained after the DAB procedure. Their mean diameter is approximately 0.25 micron. Serial sections reveal that the circular and rod-shaped peroxisomal profiles are cross and oblique sections of highly tortuous, tubular organelles exceeding 2 micron in length. In addition to tubular profiles, elongated, rectangular particles, as well as straight dumbbell-shaped organelles with distinct marginal plates are observed. They range from 900 to 1650 nm in length (mean = 1200 nm). In the flattened, thin central portion of the dumbbell-shaped particle, the peroxisomal membranes form a cisterna enclosing one or two uniformly thick marginal plates, which display a definite substructure with a periodicity of 10 nm. These findings indicate that peroxisomes in the liver of Ichthyophis exhibit a complex organization. It is suggested that the organelles undergo a specific differentiation process, morphologically characterized by the formation of enlarged segments of unusual shape.

Peroxisomes in sebaceous glands. IV. Aggregates of tubular peroxisomes in the mouse Meibomian gland

The occurrence of peroxisomes, their morphogenesis during the process of sebaceous transformation and their spatial relationship to the endoplasmic reticulum and lipid droplets were investigated by light and electron microscopy after visualization of the peroxidatic activity of catalase using an alkaline diaminobenzidine medium. The morphological alterations of peroxisomes display a characteristic sequence: During cellular differentiation, a remarkable proliferation of exclusively tubular, diaminobenzidine-reactive peroxisomes occurs. As maturation proceeds, an extensive elongation of tubular peroxisomes is seen. Concomitantly, they are densely packed in a regular, hexagonal arrangement and both the diameter and the catalase content gradually decreases. The most conspicuous feature of mature glandular cells are numerous highly organized aggregates of tubular, almost unstained peroxisomes with a diameter of 50 nm, arranged in a hexagonal pattern. They resemble adjacent tubular profiles of smooth endoplasmic reticulum. However, membrane continuities between these two compartments were never observed. During lethal disintegration peroxisomes subsequently decrease in number, probably by rapid sequestration within autophagolysosomes. The role of tubular peroxisomes in the biosynthesis of wax esters in the mouse Meibomian gland is discussed.

Peroxisomes in sebaceous glands. V. Complex peroxisomes in the mouse preputial gland: serial sectioning and three-dimensional reconstruction studies

The ultrastructure of peroxisomes in partially differentiated cells of the mouse preputial gland was investigated using serial thin sections and three-dimensional reconstruction as well as the alkaline diaminobenzidine technique for visualization of the peroxidatic activity of catalase. An analysis of serial sections indicates that the different types of intensely stained peroxisomal profiles, classified according to their shape, represent random planes through highly complex peroxisomes. These organelles exceed 4 micron in length and exhibit a focal heterogeneity with respect to their size, shape and enzyme distribution. The graphical three-dimensional reconstruction demonstrates that the most intricate peroxisomes are characterized by tortuous, elongate, and branched tubular segments of varying diameter equipped with enlarged terminal hollow-spherical structures which engulf areas of cytoplasm. A close spatial relationship is established between adjacent peroxisomes and peroxisomes and mitochondria, the latter two of which synchronously develop into highly complex structures. A close association is also observed between peroxisomes and the endoplasmic reticulum, whereby membrane continuities between the two compartments cannot be demonstrated. These observations are inconsistent with traditional concepts concerning peroxisomal shape and size, the number per cell, as well as their biogenesis from the endoplasmic reticulum. The functional significance of individual highly complex peroxisomes and their assemblage forming an extensive net-like membraneous system throughout the cell is discussed with respect to intracellular energy transport and transmembrane electron exchange.

Peroxisomes in sebaceous glands. III. Morphological similarities of peroxisomes with smooth endoplasmic reticulum and Golgi stacks in the circumanal gland of the dog

In the canine circumanal gland, the morphological alterations of peroxisomes during differentiation and maturation of the glandular cells were studied by electron microscopy, cytochemistry and freeze-etch technique. Each of the following three cell types has its own characteristic peroxisomal population: 1) The basal cell contains only a few small peroxisomes, which appear as spherical and tubular profiles showing strong DAB reaction. In the differentiating basal cells, these are joined by a few dilated, hemispherical organelles with intensely stained small marginal plates. 2) In the intermediate cell, additional to spherical and tubular peroxisomes, numerous elongated organelles with distinct marginal plates are observed, displaying weak catalase activity. 3) In the mature cell, dumbbell-shaped peroxisomes with enlarged marginal plates predominate. Serial section analysis and freeze-etching studies reveal that these dilated particles are of erythrocyte-like shape. They exhibit very weak catalase activity or do not contain any visible DAB reaction product. In their flattened, thin central portions, the membranes enclose the marginal plates and form straight cisternae, which are closely associated with adjacent fenestrated cisternae of ER on both sides, referred to as paramarginal cisternae. Dumbbell-shaped peroxisomes with their corresponding paramarginal cisternae form large peroxisome-ER-complexes. Furthermore, three to five dumbbell-shaped particles are often stacked in parallel. Only at their flat poles are the organelles in close contact with paramarginal cisternae. The observation of continuities, in particular between erythrocyte-like organelles and tubular peroxisomes in mature glandular cells, indicates the existence of a peroxisomal compartment composed of two segments in the mature stage. In freeze-etch replicas of mature glandular cells, only the dilated segments of the peroxisomal compartment can be easily recognized because of their unusual size and erythrocyte-like shape. Additionally, on the E-face of their central portion, a straight, square or rectangular area with a distinct crystalline pattern is seen, which corresponds to the marginal plate. These findings indicate that the circumanal gland of the dog offers a unique possibility to analyze the biological properties of a well-defined peroxisomal compartment.

Quantitation of catalase activity by microspectrophotometry after diaminobenzidine staining

The absorbance of the reaction product of catalase staining with diaminobenzidine is linearly proportional to enzyme activity. This is shown in semithin Epon sections of model systems containing serum albumin and catalase from bovine or guinea pig liver. Absorbance measurements were also performed on semithin sections of guinea pig liver, and from these, the activity of cytoplasmic (extraperoxisomal) catalase has been derived.

Diaminobenzidine histochemistry in light microscopy

Basically the DAB-technique localizes 3 enzymes, i.e. peroxidase, catalase, and cytochrome oxidase, but also pseudoperoxidatic activity of hemeenzymes (hemoglobin, myoglobin, etc.). Although at the ultrastructural level, i.e. in cytochemistry, the appropriate conditions for specific identification of each of these enzymatic activities have been extensively studied and reported in the literature, the subject remains open to investigation. In light microscopy DAB staining has been less thoroughly studied. Since DAB histochemistry might have practical interest in daily diagnostic pathology, it appeared worthwhile to work out a method convenient for paraffin embedded tissues. The method consisted of a prolonged incubation 48 h) of small tissue blocks, which had been prefixed for 1 h in 4% formaldehyde. Dehydration and rehydration occurred in graded ethanols; counterstain was obtained by toluidine blue. Although further experiments are needed to specify the physico-chemical conditions for the three enzymatic activities, the results are morphologically superior to that of frozen sections.

Selective cytochemical localization of peroxidase, cytochrome oxidase and catalase in rat liver with 3,3'-diaminobenzidine

In rat liver, three different enzymes with peroxidatic activity are demonstrated with modifications of the DAB-technique: peroxidase in the endoplasmic reticulum of Kupffer cells, catalase in peroxisomes and cytochrome oxidase in mitochondria. The major problem of the DAB-methods is their limited specificity so that often in tissues incubated for one enzyme the other two proteins are also stained simultaneously. We have studied the conditions for selective staining of each of these three enzymes in rat liver fixed either by perfusion with glutaraldehyde or by immersion in a modified Karnovsky's glutaraldehyde-formaldehyde fixative. The observations indicate that in perfusion fixed material selective staining can be obtained by reduction of the incubation time (5 min) and the use of optimal conditions for each enzyme. In livers fixed by immersion the distribution of the staining is patchy and irregular and usually longer incubation times (15-30 min) are required. Selective staining of peroxidase in Kupffer cells was obtained by brief incubation at room temperature in a medium containing 2.5 mM DAB in cacodylte buffer pH 6.5 and 0.02% H2O2. The exclusive staining for cytochrome oxidase in cristae of mitochondria was achieved after short incubation in 2.5 mM DAB in phosphate buffer pH 7.2 containing 0.05% cytochrome c. For selective demonstration of catalase in peroxisomes the tissue was incubated in 5 mM DAB in Teorell-Stenhagen (or glycine-NaOH) buffer at pH 10.5 and 0.15% H2O2. The prolongation of the incubation time in peroxidase medium caused marked staining of both mitochondria and peroxisomes. In the cytochrome oxidase medium longer incubations led to slight staining of peroxisomes. The catalase medium was quite selective for this enzyme so that even after incubation for 120 min only peroxisomes stained.

Peroxisome-associated aldehyde dehydrogenase in normal rat liver

We have combined subcellular fractionation and cytochemical staining techniques to study the distribution of aldehyde dehydrogenase in rat liver. In addition to confirming the mitochondrial and microsomal localization of aldehyde dehydrogenase, this combined approach has allowed us to demonstrate that peroxisome-like organelles possess significant aldehyde dehydrogenase. When peroxisomal fractions are cytochemically stained for aldehyde dehydrogenase, activity is observed along membranes of structures resembling peroxisomal ghosts. These bodies lack a matrix but many appear to enclose peroxisomal cores. Moderate to dense reaction product is also located in single membrane-limited structures present in fractions containing morphologically recognizable peroxisomes. On occasion, the osmiophilic precipitate is also present in the matrix of intact peroxisomes. The aldehyde dehydrogenase activity in these peroxisome-like organelles prefers aliphatic aldehydes, including acetaldehyde in both millimolar and micromolar concentrations, and NAD. Aromatic aldehydes and NADP are also metabolized, but to a lesser extent. These results indicate that peroxisome-like organelles contain an aldehyde dehydrogenase activity possessing properties compatible with a role in ethanol metabolism.