Microbodies of the rat renal proximal tubule: ultrastructural and cytochemical investigations

Localization of a mitochondrial type of NADP-dependent isocitrate dehydrogenase in kidney and heart of rat: an immunocytochemical and biochemical study

We studied the subcellular localization of the mitochondrial type of NADP-dependent isocitrate dehydrogenase (ICD1) in rat was immunofluorescence and immunoelectron microscopy and by biochemical methods, including immunoblotting and Nycodenz gradient centrifugation. Antibodies against a 14-amino-acid peptide at the C-terminus of mouse ICD1 was prepared. Immunoblotting analysis of the Triton X-100 extract of heart and kidney showed that the antibodies developed a single band with molecular mass of 45 kD. ICD1 was highly expressed in heart, kidney, and brown fat but only a low level of ICD1 was expressed in other tissues, including liver. Immunofluorescence staining showed that ICD1 was present mainly in mitochondria and, to a much lesser extent, in nuclei. Low but significant levels of activity and antigen of ICD1 were found in nuclei isolated by equilibrium sedimentation. Immunoblotting analysis of subcellular fractions isolated by Nycodenz gradient centrifugation from rat liver revealed that ICD1 signals were exclusively distributed in mitochondrial fractions in which acyl-CoA dehydrogenase was present. Immunofluorescence staining and postembedding electron microscopy demonstrated that ICD1 was confined almost exclusively to mitochondria and nuclei of rat kidney and heart muscle. The results show that ICD1 is expressed in the nuclei in addition to the mitochondria of rat heart and kidney. In the nuclei, the enzyme is associated with heterochromatin. In kidney, ICD1 distributes differentially in the tubule segments.

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.

Molecular organization of hepatocyte peroxisomes

The matrix of peroxisomes has been considered to be homogeneous. However, a fine network of tubules is visible in electron micrographs at very high magnification. This substructure becomes more positive in a high-contrast photocopy and with an imaging-plate method. Clofibrate, bezafibrate, and aspirin increase peroxisomes. In proliferated peroxisomes, the density of matrix is low and the fine network is more visible. The effect of proliferators is more significant in males than in females. This sex difference may involve the action of estrogen, growth hormone, cytochrome P-450 and thyroxine. Mg-ATPase is localized on the limiting membrane of peroxisomes. Even on the membrane of irregular projections of proliferated peroxisomes, Mg-ATPase is evident cytochemically. Carnitine acetyltransferase is detectable in the matrix of proliferated peroxisomes. Withdrawal of proliferators results in a rapid decrease of peroxisomes. This may indicate the existence of peroxisome suppressors. Alternatively, dynamic transformation of vesicular to tubular types in peroxisome reticulum may occur. Such transformation has been described in lysosomes and mitochondria.

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.

Detection of peroxisomes in human liver and kidney fixed with formalin and embedded in paraffin: the use of catalase and lipid beta-oxidation enzymes as immunocytochemical markers

We describe the immunocytochemical localization of four peroxisomal enzymes by light microscopy in human liver and kidney processed routinely by formalin fixation and paraffin embedding. Monospecific antisera against catalase and three enzymes of peroxisomal lipid beta-oxidation (acyl-CoA oxidase, bifunctional protein (enoyl-CoA hydratase, 3-hydroxyacyl-CoA dehydrogenase) and 3-ketoacyl-CoA thiolase) were used in conjunction with either the indirect immunoperoxidase method or the protein A-gold technique followed by silver intensification. The sections of formalin-fixed paraffin-embedded tissue had to be deparaffinized and subjected to controlled proteolysis in order to obtain satisfactory immunostaining. Under the conditions employed, peroxisomes were distinctly visualized in liver parenchymal cells with no reaction in bile duct epithelial or sinusoidal lining cells. In the kidney, peroxisomes were confined to the proximal tubular epithelial cells with negative staining of glomeruli, distal tubules and collecting ducts. A positive immunocytochemical reaction was obtained even in paraffin blocks stored for several years. The method offers a simple approach for detection of peroxisomes and evaluation of their various enzyme proteins in material processed routinely in histopathology laboratories and should prove useful in the investigation of the role of peroxisomes in human pathology for both prospective and retrospective studies.

Immunocytochemical demonstration of peroxisomal enzymes in human kidney biopsies

Peroxisomes are particularly abundant in the proximal tubules of the mammalian kidney. We describe the immunocytochemical localization of catalase and three peroxisomal lipid beta-oxidation enzymes: acyl-CoA oxidase, bifunctional protein (enoyl-CoA hydratase, 3-hydroxyacyl-CoA dehydrogenase) and 3-ketoacyl-CoA thiolase, in human renal biopsies fixed with glutaraldehyde and embedded in Epon. For light microscopy of semithin sections, satisfactory immunostaining required removal of the resin and controlled proteolytic digestion followed by the indirect immunoperoxidase technique. Brief etching of ultrathin sections with alkoxide followed by the protein A-gold method were used for electron microscopic localization of the enzymes. The immunoreactive peroxisomes were distinctly visualized in proximal tubular epithelial cells with no staining of any other cell organelles. The results establish the presence of catalase and of peroxisomal lipid beta-oxidation system proteins in human kidney. The immunocytochemical procedure described herein provides a simple approach for the investigation of peroxisomal structure and function in human renal biopsies processed for ultrastructural studies.

Rat urinary kallikrein localization in kidney: effects of fixation

The influence of fixation on the immunocytochemical localization of tissue kallikrein in the kidney has been evaluated using both monoclonal and polyclonal antibodies. These studies have provided several results relevant to kallikrein localization in kidney: (1) the intensity and distribution of immunostaining with both polyclonal and monoclonal anti-kallikrein antibodies is fixation-dependent; (2) the most intense and consistent localizations of kallikrein are in the connecting tubule and the cortical collecting duct of the nephron; (3) kallikrein-like immunoreactivity is seen in proximal tubules with polyclonal but not with non-cross-reactive monoclonal antibodies; and (4) fixatives which disrupt membranes reveal a kallikrein-like antigen in straight tubules of the outer medulla. However, immunostaining with monoclonal antibodies indicates that much of the observed immunostaining at this site probably represents cross-reactivity with another member of the kallikrein family of enzymes.

Immunoelectron microscopic localization of D-amino acid oxidase in rat kidney and liver

The intracellular localization of D-amino acid oxidase in rat kidney and liver has been investigated using the indirect immunogold postembedding technique. Different fixation and embedding conditions for optimal preservation of antigenicity and fine structure have been tested. Immunolabelling was possible only in tissues embedded in polar resins (glycol methacrylate and Lowicryl K4M). In kidney the enzyme was demonstrable only in the peroxisomes of the proximal tubule, where it was associated with the peroxisome core. The enzyme was present in all the peroxisomes of the proximal tubule and appeared to be codistributed with catalase. Control experiments and quantitative analysis confirmed the specificity of the D-amino acid oxidase immunolocalization. All the other cells in kidney failed to demonstrate any labelling. In liver, the immunolabelling was present in the matrix of the hepatocyte peroxisomes, whereas no traces of the enzyme were found in the nucleoid. The intensity of the immunolabelling in liver peroxisomes was lower than in kidney. No specific labelling was observed in cells other than hepatocytes.

Electron microscopic cytochemical localization of alpha-hydroxyacid oxidase in rat kidney cortex. Heterogeneous staining of peroxisomes

The substrate specificity of alpha-hydroxyacid oxidase in the rat kidney has been investigated cytochemically by the cerium technique and biochemically with a luminometric assay applied to isolated renal peroxisomes. Rat kidneys were fixed by perfusion via the abdominal aorta with a low concentration (0.25%) of glutaraldehyde. Vibratome sections were incubated for 60 min at 37 degrees C in a medium containing 3 mM CeCl3, 100 mM NaN3 and 5 mM of an alpha-hydroxyacid in 0.1 M Pipes or 0.1 M Tris-maleate buffer both adjusted to pH 7.8. Ten aliphatic alpha-hydroxyacids with chain lengths between 2 and 8 carbon atoms and two aromatic substrates were tested. The alpha-hydroxyacid oxidase in the kidney exhibited a markedly different substrate specificity than the corresponding enzyme in the liver. Thus glycolate gave a negative reaction while two aromatic substrates, mandelic acid and phenyllactic acid, stained prominently. With aliphatic substrates a stronger reaction was obtained in Pipes than in the Tris-maleate buffered incubation media. The best reaction in the kidney was obtained with hydroxybutyric acid. These cytochemical findings were confirmed by the luminometric determination of the oxidase activity in isolated purified peroxisome fractions. By electron microscopy the electron dense reaction product of cerium perhydroxide was found in the matrix of peroxisomes in the proximal tubules. The intensity of reaction varied markedly in neighbouring epithelial cells but also in different peroxisomes within the same cell. Thus heavily stained particles were seen next to lightly reacted ones. These observations establish the substrate specificity of alpha-hydroxyacid oxidase in the rat kidney and demonstrate the marked heterogeneity in the staining of renal peroxisomes for this enzyme.

Peroxisomes in human foetal kidney: variations in size and number during development

The kidneys of 15 human foetuses (10-18 weeks of age) were used for morphometric studies on peroxisomes during gestational development and in organ culture. The catalase positive organelles revealed by DAB were round to ovoid with a granular matrix delimited by a membrane occasionally deformed by marginal plates. Generally, the distribution was uniform in cells of proximal tubules. In the same cell, size and density varied. The number fluctuated from cell to cell. No significant difference in the mean diameter was observed from the 10th to 18th weeks of gestation, although the mean value (0.36 +/- 0.1 micron) was significantly less than the adult figure. These results indicate that size modifications might occur later on in gestation or after birth to reach the adult value. During the studied period, the mean number of peroxisomes per 100 micron2 of surface area did not differ significantly from that of the 10-12 week group (10.5 +/- 1.97). No important changes of peroxisome morphology in kidney explants cultured for 7 days were noticed on day 3-4. Thereafter, the shape of many peroxisomes became elongated or irregular; marginal plates were frequent. A decrease in the diameter of peroxisomes began at day 4, became significant on day 5 and more accentuated on day 7. In addition, as the culture matured, there was a progressive reduction in catalase activity, revealed by a diminished density of the peroxisomal matrix. The number of DAB positive organelles per surface area decreased steadily with culture age, and significantly on day 2 (p less than 0.01) to become drastically low on day 5 and negligible on day 7.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunocytochemical demonstration of serine: pyruvate amino-transferase in peroxisomes and mitochondria of rat kidney

The light- and electron-microscopic localization of serine: pyruvate aminotransferase (SPT) in rat kidney was studied using immunoenzyme and protein A-gold techniques. Rat kidneys were fixed by perfusion through the abdominal aorta and small tissue slices were embedded in Epon, Lowicryl K4M, or LR Gold. The Epon was removed from the semithin sections, which were then stained using the immunoenzyme technique. Ultrathin sections of Lowicryl K4M- or LR gold-embedded materials were labeled using the protein A-gold technique. At light microscopy, discrete granular reaction deposits were exclusively present in the proximal tubule, all of whose segments were positive for SPT. A weakly positive reaction was observed in the distal tubules. At electron microscopy, gold particles indicating the antigenic sites for SPT were confined to the peroxisomes and mitochondria. The labeling intensity of both organelles was dependent on the embedding resins used. The labeling of Lowicryl K4M-embedded material was weaker than that of LR gold-embedded material; Quantitative analysis confirmed this result. Our results indicate that, in rat kidney, the main intracellular sites for SPT are peroxisomes and mitochondria of the proximal tubule.

Light and electron microscopic localization of L-alpha-hydroxyacid oxidase in rat kidney revealed by immunocytochemical techniques

Light and electron microscopic localization of L-alpha-hydroxyacid oxidase (L-HOX) in rat kidney was studied by means of immunocytochemical techniques. Isozymes A and B of L-HOX were purified from rat liver and kidney, respectively. The apparent molecular weights of the subunits of the isozymes A and B were 35,800 and 33,500 daltons, respectively, by a slab gel electrophoresis. Antibodies to the isozymes were raised in rabbits. Anti(isozyme A) is not cross-reactive with the isozyme B and vice versa anti(isozyme B) not with the isozyme A. Using anti-isozyme B, semithin sections of Epon-embedded material and ultrathin sections of Lowicryl K4M-embedded material were stained by immunoenzyme and protein A-gold techniques, respectively. By light microscopy, fine discrete granular staining was noted in proximal tubules, but not in distal tubules including thick and thin limbs of Henle and collecting tubules. By electron microscopy, gold particles representing the antigen sites for L-HOX B were confined exclusively to peroxisomes, in which most of the gold particles were localized in electron dense peripheral matrix, but little in central matrix with low electron density. The results indicate that L-HOX B does not homogeneously distribute in peroxisomes of rat kidney but might be associated with some substructure within peroxisome matrix.

Histochemical, autoradiographic and electron microscopic investigations of the renal proximal tubule of male and female rats after castration

After castration of 90-day-old male and female rats, changes appear in the renal proximal tubule. A distinction can be made between early changes (up to 10th postoperative day) and later changes (20th-30th postoperative day). Between the 3rd and 5th day after castration the kidney of the females shows an increase in free estrogen receptors (biochemical studies) which are localized in the pars contorta of the proximal tubule (autoradiographic studies), while the male kidney shows a marked increase in urinary protein excretion up to the 10th day after castration. Proximal tubule changes detectable histochemically and electron microscopically do not appear until day 20 or 30 after castration. The results of castration are similar in segments S1 and S2. By days 20 and 30 after castration there is a decrease in the activity of lysosomal enzymes (acid phosphatase, acid beta-galactosidase). Electron microscopy shows a conspicuous decrease in the number of giant lysosomes (mainly in females) and apical vacuoles (mainly in males). A marked increase in the number of lysosomes is found in the S3 segment; females always have more lysosomes than males. The number of peroxisomes is also greatly increased; they appear circular in the females but can assume bizarre shapes in the males. Lipid droplets appear in the basal region of the tubule cell of segments S2 and S3 in the males. The sex differences are preserved in all segments even after castration and become even more pronounced in the S3 segment.

Cytochemical localization of catalase and several hydrogen peroxide-producing oxidases in the nucleoids and matrix of rat liver peroxisomes

The distribution of catalase, amino acid oxidase, alpha-hydroxy acid oxidase, urate oxidase and alcohol oxidase was studied cytochemically in rat hepatocytes. The presence of catalase was demonstrated with the conventional diaminobenzidine technique. Oxidase activities were visualized with methods based on the enzymatic or chemical trapping of the hydrogen peroxide produced by these enzymes during aerobic incubations. All enzymes investigated were found to be present in peroxisomes. Catalase activity was found in the peroxisomal matrix, but also associated with the nucleoid. After staining for oxidase activities the stain deposits occurred invariably in the peroxisomal matrix as well as in the nucleoids. In all experiments the activity of both catalase and the oxidases was confined to the peroxisomes. The presence of a hydrogen peroxide-producing alcohol oxidase was demonstrated for the first time in peroxisomes in liver cells. The results imply that the enzyme activity of the nucleoids of rat liver peroxisomes is not exclusively due to urate oxidase. The nucleoids obviously contain a variety of other enzymes that may be more or less loosely associated with the insoluble components of these structures.