OAT / Ornithine aminotransferase, mitochondrial · IHC design guide

Design Immunohistochemistry for OAT

Plan chromogenic OAT IHC using high enterocyte staining in duodenum and small intestine as a reference (HPA tissue IHC). This guide covers paraffin-section antibody conditions (datasheet A01126-2) and scoring of granular cytoplasmic staining (HPA tissue IHC).

Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use

Immunohistochemistry protocol sheet for OAT (IHC for OAT): expected localisation Granular cytoplasm in tissue (HPA tissue IHC); mitochondrial matrix expected (UniProt), antibody A01126-2, validated IHC image, and IHC protocol steps — Printable **OAT** IHC protocol sheet — expected localisation Granular cytoplasm in tissue (HPA tissue IHC); mitochondrial matrix expected (UniProt), antibody A01126-2, controls and protocol steps. Open the full OAT IHC guide →

Navigate to: Protocols Staining pattern Controls Antibodies

OAT Immunohistochemistry Experimental Design Guide

Expected localisation, validated protocols, controls and antibodies — the at-a-glance facts below, then the full design guide.

Must know before staining

	Expected localisation	Granular cytoplasm in tissue (HPA tissue IHC); mitochondrial matrix expected (UniProt)
	Staining pattern	Most cells show granular cytoplasmic staining (HPA tissue IHC)
	Antigen retrieval	EDTA pH 8.0 HIER, heat-mediated (datasheet A01126-2)
	Positive control ⓘ	Duodenum+4 more · see all
	Negative control ⓘ	Adipose tissue+4 more · see all

Important caveats

Reasons your staining may differ from the expected pattern.

	Fixation	Keep formalin fixation consistent across sections. (standard IHC practice; not target-specific)
	Caveat	Hepatocytes stain low while intestinal enterocytes stain high (HPA tissue IHC)
	Regulation	Intestine-enhanced RNA expression (HPA tissue RNA)
	Isoform / epitope	2 isoforms; N-termini differ; epitope unknown (UniProt)

Section 1

Recommended OAT IHC & IF Protocols

The catalog antibody has an IHC-P protocol (datasheet: A01126-2). The published examples cover liver sections (PMC9056925) and lung tissue with BALF cells (PMC10907606).

Recommended immunohistochemistry (IHC-P) protocol parameters
Sample	Paraffin-embedded human lung cancer tissue; fixative not specified (datasheet A01126-2)
Fixation	Image fixative and duration unreported (datasheet A01126-2); verify before use.
Sectioning	4–5 µm sections on charged slides (standard)
Deparaffinisation	Xylene, graded ethanol series to water (standard)
Antigen retrieval	Heat retrieval: EDTA pH 8.0 (datasheet A01126-2); 20 min, 95–100 °C (standard)
Peroxidase block	3% H2O2, 10 min, room temperature (standard)
Blocking	10% goat serum (datasheet A01126-2)
Primary antibody	Rabbit anti-OAT, 2-5μg/ml (datasheet A01126-2)
Primary incubation	Overnight at 4 °C (datasheet A01126-2)
Detection	Streptavidin-biotin complex (SABC), DAB chromogen (datasheet A01126-2)
Counterstain	Hematoxylin, blue, dehydrate and mount (standard)
Expected result	OAT-positive staining in enterocytes of duodenum (HPA tissue IHC: High). HPA tissue profile: Cytoplasmic expression with a granular pattern in most cells. No signal in the no-primary control.

💡Decision noteStart with heat-mediated EDTA pH 8.0 retrieval (datasheet: A01126-2); the liver paper does not specify retrieval conditions (PMC9056925), and the lung paper does not report retrieval (PMC10907606).

Section 2

What Is the Expected OAT Staining Pattern?

OAT is a mitochondrial matrix enzyme with no transmembrane segment (UniProt P04181). In paraffin section IHC, expect granular cytoplasmic staining, strongest in duodenal and small intestinal enterocytes (HPA: High in both). HPA rates its tissue staining Enhanced, reflecting high consistency between antibody staining and RNA expression (HPA: reliability description). Assess the named cell population rather than assigning one intensity to an entire tissue.

What am I looking at on my slide?
Granular cytoplasmic staining is strong in intestinal enterocytes.	This matches the reported tissue pattern and High enterocyte staining (HPA: tissue IHC). The granular appearance is consistent with a mitochondrial matrix protein (UniProt P04181: subcellular location). Judge intensity against nearby cells and the same detection run; HPA levels describe observed staining, not a required numerical score.
Signal is mainly nuclear, membranous, or uniformly fills the cytoplasm.	This departs from the granular cytoplasmic IHC profile (HPA: tissue IHC). Check morphology, counterstain, and controls before calling it OAT. HPA also reports an additional nucleoplasmic location in ICC-IF (HPA: subcellular); that observation alone does not make predominantly nuclear chromogenic IHC an expected tissue pattern.
Strong signal appears in an HPA-listed undetected cell population.	For example, adipocytes are Not detected in adipose tissue (HPA: tissue IHC). Consider cross-reactivity or endogenous chromogenic activity and compare with a no-primary control (general IHC practice). The HPA designation applies to the specified cells; it does not establish that every cell in that section must be blank.
A broad, diffuse deposit covers cells and surrounding tissue.	This obscures the reported granular cytoplasmic pattern (HPA: tissue IHC). Review blocking, washes, detection chemistry, and the no-primary control (general IHC practice). Do not score diffuse color as OAT merely because the section includes an HPA-positive tissue.
Enterocytes show no discernible signal in a designated positive section.	Duodenal and small intestinal enterocytes are High in the HPA tissue record (HPA: tissue IHC). Recheck section identity, primary antibody performance, retrieval, and detection with a working positive control (general IHC practice). A failed run cannot establish that OAT is absent from the tested specimen.

💡Expected OAT appearanceCall a positive IHC result when enterocytes show strong granular cytoplasmic staining (HPA: High; tissue IHC), consistent with mitochondrial matrix OAT (UniProt P04181); isolated strong membrane staining or featureless diffuse color is suspect against that pattern (HPA: tissue IHC).

How each factor affects the staining
Cell population and tissue	HPA reports High enterocyte staining in duodenum and small intestine, Medium staining in several other specified cell populations, and Low hepatocyte staining (HPA: tissue IHC). Choose and score controls by cell type; a weak liver section is a poor benchmark for the expected enterocyte intensity.
Intracellular location	OAT resides in the mitochondrial matrix and has no transmembrane segment (UniProt P04181). Expect a granular cytoplasmic IHC pattern (HPA: tissue IHC). HPA's additional nucleoplasmic ICC-IF finding is method-specific context, not evidence for a predominantly nuclear tissue IHC call (HPA: subcellular).
Antibody validation	HPA lists Enhanced IHC status for HPA040098 and CAB033576 (HPA: antibodies). Its overall tissue reliability is Enhanced (HPA: tissue IHC). These support comparison with the published pattern but do not prove that an unlisted catalog antibody, dilution, or detection system behaves identically.
Protein processing and isoforms	UniProt lists hepatic-form residues 26–439, renal-form residues 36–439, and two isoforms (UniProt P04181). If staining differs across specimens, check the chosen antibody's documented epitope before proposing a form-specific explanation; no epitope or form-specific IHC performance is supplied.
Retrieval and detection setup	Retrieval, primary concentration, blocking, and chromogen development require run controls and local optimization (general IHC practice). Neither source supplies an OAT-specific retrieval condition or fixation-sensitivity result; do not infer one from mitochondrial location, modifications, or HPA tissue intensity (UniProt P04181; HPA: tissue IHC).

Why is my staining missing, weak or wrong?
Situation	Likely cause	Next action
High enterocyte control is blank.	The run may have failed at primary binding, retrieval, or detection (general IHC practice); HPA reports High staining in these cells (HPA: tissue IHC).	Verify the control's identity and preserved morphology, then check reagent activity and each detection step using the antibody's documented IHC-P instructions (general IHC practice). Do not infer an OAT-specific fixation failure from this result.
Granular color is too faint to distinguish from counterstain.	Insufficient developed signal or heavy counterstain can hide a cellular pattern (general IHC practice).	Compare with the High enterocyte control (HPA: tissue IHC); adjust development or counterstain under a controlled run (general IHC practice). Record the change before comparing specimen intensities.
No-primary control develops the same color as test sections.	Primary-independent background or endogenous detection activity is plausible (general IHC practice).	Check detection-only reagents and apply the appropriate endogenous-activity block for the enzyme system in use (general IHC practice). Reassess the reported granular cytoplasmic pattern only after background is controlled (HPA: tissue IHC).
Strong color appears in adipocytes or other undetected HPA cell types.	Cross-reactivity or detection background is possible; adipocytes are Not detected in HPA's tissue record (HPA: tissue IHC).	Compare the exact cell population with its HPA designation and a no-primary control (HPA: tissue IHC; general IHC practice). If the discrepancy persists, verify with an independently validated antibody (general IHC practice).
The signal is predominantly nuclear.	This conflicts with the granular cytoplasmic tissue pattern (HPA: tissue IHC), although an additional nucleoplasmic ICC-IF location is reported (HPA: subcellular).	Inspect focus, counterstain, and control sections; compare localization with a second validated reagent if available (general IHC practice). Report the compartment and method explicitly rather than converting the ICC-IF observation into an IHC expectation.
All cells have diffuse brown staining that conceals cell boundaries.	Excess detection development, inadequate washing, or nonspecific reagent binding may produce diffuse deposit (general IHC practice).	Compare no-primary and positive controls, then optimize washing, blocking, and chromogen development (general IHC practice). Score OAT only where the cellular pattern remains interpretable against HPA's granular cytoplasmic profile (HPA: tissue IHC).

Source: UniProt P04181 Human Protein Atlas tissue Human Protein Atlas subcellular

Experiment evidence

IHC & IF images showing OAT staining

IHC analysis of Ornithine Aminotransferase/OAT using anti-Ornithine Aminotransferase/OAT antibody (A01126-2). Ornithine Aminotransferase/OAT was detected in a paraffin-embedded section of human lung cancer tissue. Heat mediated antigen retrieval was performed in EDTA buffer (pH 8.0, epitope retrieval solution). The tissue section was blocked with 10% goat serum. The tissue section was then incubated with 2 μg/ml rabbit anti-Ornithine Aminotransferase/OAT Antibody (A01126-2) overnight at 4°C. Biotinylated goat anti-rabbit IgG was used as secondary antibody and incubated for 30 minutes at 37°C. The tissue section was developed using Strepavidin-Biotin-Complex (SABC) (Catalog # SA1022) with DAB as the chromogen.

A01126-2 · IHCIHC analysis of Ornithine Aminotransferase/OAT using anti-Ornithine Aminotransferase/OAT antibody (A01126-2). Ornithine Aminotransferase/OAT

Formalin-fixed and paraffin-embedded human brain tissue reacted with OAT Antibody (N-term), which was peroxidase-conjugated to the secondary antibody, followed by DAB staining. This data demonstrates the use of this antibody for immunohistochemistry; clinical relevance has not been evaluated.

A01126-1 · IHCFormalin-fixed and paraffin-embedded human brain tissue reacted with OAT Antibody (N-term), which was peroxidase-conjugated to the secondary

Fluorescent image of A549 cell stained with OAT Antibody (N-term). A549 cells were fixed with 4% PFA (20 min), permeabilized with Triton X-100 (0. 1%, 10 min), then incubated with OAT primary antibody (1:25, 1 h at 37℃). For secondary antibody, Alexa Fluor® 488 conjugated donkey anti-rabbit antibody (green) was used (1:400, 50 min at 37℃). Cytoplasmic actin was counterstained with Alexa Fluor® 555 (red) conjugated Phalloidin at 37℃). OAT immunoreactivity is localized to Mitochondrion significantly.

A01126-1 · IFFluorescent image of A549 cell stained with OAT Antibody (N-term). A549 cells were fixed with 4% PFA (20 min), permeabilized with Triton X-1

HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000065154-OAT/tissue/cerebral+cortex#imid_11027803

HPA · DuodenumHuman Protein Atlas IHC, Duodenum. Source: https://www.proteinatlas.org/ENSG00000065154-OAT/tissue/duodenum#imid_11026620

HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000065154-OAT/tissue/colon#imid_11026613

HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000065154-OAT/tissue/liver#imid_11026614

HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody HPA064742; green = OAT, blue = nucleus, red = microtubules.

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Real IHC / IF data behind the staining-pattern expectations in this section.

Sample controls for OAT IHC & IF

🧪Run duodenum first and require staining in enterocytes (HPA: High in duodenum enterocytes); use adipose tissue as the negative and assess adipocytes (HPA: Not detected in adipocytes). No verified OAT-negative cell type within duodenum is supplied, so unstained neighboring cells can indicate background but cannot serve as a validated biological negative.

Positive control tissue: Duodenum (Enterocytes, HPA High)

Negative control tissue: Adipose tissue (HPA Not detected)

ICC-IF cell lines (HPA subcellular resource): HPA ICC-IF images show OAT in A-431, HEK293, U2OS, with annotated localisation: Mitochondria (supported) (HPA subcellular).

Technical controls: Include a no-primary, secondary-only slide and a concentration-matched nonimmune rabbit IgG isotype control (caption: rabbit primary antibody); use OAT-knockout material as a biological specificity control (standard IHC practice). For duodenum, check endogenous peroxidase and biotin background before interpreting DAB staining (standard IHC practice; caption: SABC/DAB detection).

⚠️Feasibility: A target-specific fixation window or fixation effect is unreported, and the selected-SKU caption does not state a fixative (caption: fixative not stated). The caption reports heat retrieval in EDTA at pH 8.0, but does not establish that retrieval is required; no supplied comparison establishes whether frozen sections or IF are easier (caption: paraffin-section IHC; HPA: ICC-IF images). In duodenum, endogenous biotin can complicate interpretation with the caption’s SABC detection, so assess background on the control slides (standard IHC practice; caption: SABC/DAB detection).

HPA tissue IHC evidence for OAT

Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Enhanced — High consistency between antibody staining and RNA expression data.). Rows are taken directly from the HPA tissue chart — click any row's HPA link to view the source.

Positive expression · recommended positive controls

Tissue	Cell type	Level	Evidence	Source
Duodenum	Enterocytes	High	Protein (IHC)	HPA →
Small intestine	Enterocytes	High	Protein (IHC)	HPA →
Adrenal gland	Glandular cells	Medium	Protein (IHC)	HPA →
Breast	Glandular cells	Medium	Protein (IHC)	HPA →
Bronchus	Respiratory epithelial cells	Medium	Protein (IHC)	HPA →

Undetected expression · recommended negative controls

Tissue	Cell type	Level	Evidence	Source
Adipose tissue	Adipocytes	Not detected	Protein (IHC)	HPA →
Appendix	Endocrine cells	Not detected	Protein (IHC)	HPA →
Cerebellum	Cells in granular layer	Not detected	Protein (IHC)	HPA →
Colon	Endocrine cells	Not detected	Protein (IHC)	HPA →
Epididymis	Glandular cells	Not detected	Protein (IHC)	HPA →

Section 3

Advanced OAT IHC Tips

For OAT IHC in paraffin sections, troubleshoot retrieval, staining pattern, and controls together; interpret chromogenic signal against its expected mitochondrial distribution.

How should I optimize retrieval when OAT staining is weak in paraffin sections?

Start with heat-mediated EDTA retrieval at pH 8.0 for paraffin OAT IHC (datasheet A01126-2). The selected tissue image used this retrieval before overnight incubation with 2 μg/ml primary antibody at 4°C (datasheet A01126-2). If signal is weak, compare retrieval heating times on adjacent sections while holding antibody concentration and detection constant (standard IHC practice). Include a known positive compartment, such as duodenal enterocytes, and a no-primary control in the same run (HPA: High in duodenal enterocytes; standard IHC practice). Excessively diffuse staining or damaged morphology after longer heating argues for shortening retrieval before increasing detection strength (standard IHC practice).

Could fixation explain weak or uneven OAT staining?

Target-specific OAT sensitivity to fixation is unknown: the selected paraffin-section caption does not state a fixative (datasheet A01126-2). Record the fixative and fixation interval for every block, then compare sections with similar processing histories before changing antibody conditions (standard IHC practice). For newly collected material, use a consistent, documented formalin fixation workflow and avoid treating differences in staining as biological until processing is matched (standard IHC practice). Keep retrieval at EDTA pH 8.0 during that comparison (datasheet A01126-2). Use preserved morphology and a same-run positive tissue control to distinguish processing failure from a genuinely weak sample signal (standard IHC practice).

Which staining pattern supports specific OAT detection?

Expect predominantly granular cytoplasmic staining in tissue sections, consistent with OAT residing in the mitochondrial matrix (HPA: granular cytoplasmic expression in most cells; UniProt P04181: mitochondrial matrix). Assess granules within intact cell borders and compare their distribution with a positive tissue control before scoring faint diffuse color (standard IHC practice; HPA: High in duodenal enterocytes). OAT has no annotated transmembrane segment, so a crisp plasma-membrane rim alone would be unexpected (UniProt P04181 topology). The subcellular atlas also reports an additional nucleoplasmic location in cell imaging, but that does not establish nuclear staining as the expected paraffin-IHC pattern (HPA subcellular: approved nucleoplasm). Review nuclear-only DAB against no-primary and morphology controls (standard IHC practice).

Can processing or isoforms change what this antibody detects?

OAT has 2 annotated isoforms and mature hepatic and renal chains beginning at residues 26 and 36, respectively (UniProt P04181 processing and isoforms). The supplied caption does not identify the antibody epitope, so neither chain coverage nor isoform selectivity can be inferred from staining (datasheet A01126-2). Record the exact antibody lot and obtain its immunogen or epitope information before attributing a tissue difference to processing (standard IHC practice). OAT also has annotated acetylated and succinylated residues, but their effects on this antibody are unestablished (UniProt P04181 modified residues). Compare adjacent sections under the same EDTA pH 8.0 retrieval before interpreting a changed pattern (datasheet A01126-2; standard IHC practice).

How can IF help assess an ambiguous chromogenic OAT pattern?

For the separate IF/ICC workflow, multiplex OAT with a marker identifying the expected cell population, such as enterocytes when examining duodenum (HPA: High in duodenal enterocytes; standard IF practice). Choose fluorophores after checking tissue autofluorescence in an unstained section, favoring channels with clearer separation from that background (standard IF practice). OAT is a mitochondrial-matrix protein without a transmembrane segment, so optimize permeabilisation for access through cellular and mitochondrial membranes; the antibody’s epitope is unspecified (UniProt P04181 localisation and topology; datasheet A01126-2). A mitochondrial countermarker can test overlap, while the reported additional nucleoplasmic location warrants separate assessment rather than automatic rejection (HPA subcellular: supported mitochondria, approved nucleoplasm). Keep IF conclusions distinct from chromogenic intensity scores (standard assay practice).

What should I change when DAB background obscures OAT granules?

First inspect no-primary and secondary-only controls for color caused by the detection system rather than primary-antibody binding (standard IHC practice). The selected example used 10% goat serum blocking, 2 μg/ml primary antibody overnight at 4°C, and a biotin-based DAB detection sequence (datasheet A01126-2). Include a peroxidase block and check endogenous biotin background when using that sequence (standard chromogenic IHC practice). If controls are clean but tissue is uniformly brown, compare lower primary concentrations or shorter chromogen development on adjacent sections (standard IHC practice). Preserve granular cytoplasmic detail when selecting conditions, since that is the reported tissue pattern (HPA: granular cytoplasmic expression).

How should I score heterogeneous OAT staining across a section? ⚠ ANSWER MARKED FOR VERIFICATION

Define the scored cell population and exclude folds, necrosis, and section edges before measuring signal (standard IHC practice). For intact cells, report the percentage positive and an H-score from 0–300 using intensity grades 0–3, with thresholds fixed across cases (standard IHC practice). Normalize positive-cell counts to the number of eligible cells; if measuring stained area or cell density, report the sampled viable tissue area in mm² (standard IHC practice). Score granular cytoplasmic signal separately from diffuse or nuclear-only color because the reported tissue pattern is granular cytoplasmic (HPA: tissue IHC profile). Use same-run reference sections to monitor variation in retrieval and DAB development (standard IHC practice).

When is a positive OAT stain likely to be artefactual?

A convincing result places granular cytoplasmic signal in intact cells and tracks expected positive populations, such as duodenal enterocytes (HPA: granular tissue pattern; HPA: High in duodenal enterocytes). Isolated membrane-rim staining conflicts with OAT’s mitochondrial-matrix location and lack of a transmembrane segment (UniProt P04181 localisation and topology). Treat edge-restricted color, necrotic deposits, and signal reproduced in no-primary controls as potential technical artefacts (standard IHC practice). Endogenous peroxidase can create DAB color, so review the peroxidase block and detection controls before calling an unexpected cell population positive (standard chromogenic IHC practice). Apparent absence in a test sample needs a same-run positive control before a biological conclusion (standard IHC practice).

Boster reagents

Best OAT / Ornithine aminotransferase, mitochondrial IHC Antibodies

Both antibodies have human tissue IHC images (catalog IHC captions); A01126-1 also has an A549 cell IF image (A01126-1 IF caption). Both list human, mouse, and rat reactivity (catalog).

Real IHC data

Anti-ornithine aminotransferase/OAT Antibody ®

Cat # A01126-2

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Real IHC data Formalin-fixed and paraffin-embedded human brain tissue reacted with OAT Antibody (N-term), which was peroxidase-conjugated to the secondary antibody, followed by DAB staining. This data demonstrates the use of this antibody for immunohistochemistry; clinical relevance has not been evaluated.

Anti-OAT Antibody (N-term)

Cat # A01126-1

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A01126-2 shows IHC in paraffin-embedded human lung cancer, rectal cancer, testicular cancer, and small intestine (A01126-2 IHC captions). A01126-1 shows DAB IHC in formalin-fixed, paraffin-embedded human brain and IF in A549 cells (A01126-1 IHC and IF captions).

Which to pick: For tissue IHC, choose A01126-2 when its broader set of human paraffin-section examples is useful; its IHC captions do not report a fixative (A01126-2 IHC captions). For IF/ICC, choose A01126-1: IF is listed at 1:10–1:50, with an A549 cell image at 1:25 (A01126-1 catalog and IF caption). For mouse or rat work, A01126-1 is a polyclonal candidate listing IHC-P, IF, and both species, but its supplied IHC and IF images show human samples only (A01126-1 catalog, IHC caption, and IF caption).

Each figure is that product's own IHC / IF validation image from its datasheet.

References

UniProt Consortium. UniProt entry P04181 (OAT_HUMAN, Ornithine aminotransferase, mitochondrial).
Human Protein Atlas. OAT tissue IHC expression (reliability: Enhanced).
Human Protein Atlas. OAT subcellular location (ICC-IF): Mainly localized to the mitochondria. In addition localized to the nucleoplasm..
Human Protein Atlas. OAT antibody validation summary (3 antibodies).
Ornithine aminotransferase and carbamoyl phosphate synthetase 1 involved in ammonia metabolism serve as novel targets for early stages of gastric cancer. Journal of clinical laboratory analysis 2022 — PMC9551119.
MRI contrast enhancement of liver pre-neoplasia using iron-tannic nanoparticles. RSC advances 2020 — PMC9056925.
Hypoxic-ischemic injury decreases anxiety-like behavior in rats when associated with loss of tyrosine-hydroxylase immunoreactive neurons of the substantia nigra. Brazilian journal of medical and biological research = Revista brasileira de pesquisas medicas e biologicas 2012 — PMC3854134.
Role of lung ornithine aminotransferase in idiopathic pulmonary fibrosis: regulation of mitochondrial ROS generation and TGF-β1 activity. Experimental & molecular medicine 2024 — PMC10907606.
PubMed PMID:3456579 — UniProt-cited evidence.
PubMed PMID:3816496 — UniProt-cited evidence.
PubMed PMID:2507357 — UniProt-cited evidence.