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CASR / Extracellular calcium-sensing receptor · IHC design guide
Design Immunohistochemistry for CASR
Plan CASR staining in paraffin sections using its observed membranous and cytoplasmic tissue pattern (HPA tissue IHC). This guide covers fixation, controls and scoring for the IHC-validated antibody.
Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use
CASR 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 | Membranous and cytoplasmic staining (HPA tissue IHC) | |
| Staining pattern | Islets, parathyroid cells and some renal tubules stain (HPA tissue IHC) | |
| Antigen retrieval | EDTA pH 8.0 HIER, heat-mediated (datasheet PB9924) | |
| Positive control | Kidney+2 more · see all | |
| Negative control | Adipose tissue+4 more · see all |
Important caveats
Reasons your staining may differ from the expected pattern.
| Fixation | Keep fixation consistent across sections (standard IHC practice; not target-specific); Matched tissue-IHC evidence does not establish the fixation claim. Validate the specimen-specific method before use. (selected-SKU IHC image PB9924) | |
| Caveat | Only a subset of renal tubules stains (HPA tissue IHC) | |
| Regulation | Expression regulation is unreported (UniProt) | |
| Isoform / epitope | 2 isoforms; check whether the epitope is extracellular or cytoplasmic (UniProt) |
Section 1
Recommended CASR IHC & IF Protocols
The catalog antibody has an IHC-P protocol (datasheet: PB9924). The published protocols below provide CASR staining conditions for mouse kidney and parathyroid, lung adenocarcinoma, and endometrial tissue (PMC8935519; PMC4632928; PMC5773571; PMC7330125).
| Sample | Paraffin-embedded mouse kidney tissue; fixative not specified (datasheet PB9924) |
| Fixation | Image fixative and duration unreported (datasheet PB9924); 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 PB9924); 20 min, 95–100 °C (standard) |
| Peroxidase block | 3% H2O2, 10 min, room temperature (standard) |
| Blocking | 10% goat serum (datasheet PB9924) |
| Primary antibody | Rabbit anti-CASR, 0.5-1μg/ml (datasheet PB9924) |
| Primary incubation | Overnight at 4 °C (datasheet PB9924) |
| Detection | Streptavidin-biotin complex (SABC), DAB chromogen (datasheet PB9924) |
| Counterstain | Hematoxylin, blue, dehydrate and mount (standard) |
| Expected result | CASR-positive staining in distal tubules of kidney (HPA tissue IHC: High). HPA tissue profile: Cytoplasmic and membranous expression in islets of Langerhans, parathyroid gland and in a subset of renal tubules. No signal in the no-primary control. |
💡Decision noteStart with heat-mediated EDTA pH 8.0 retrieval for the catalog antibody (datasheet: PB9924); optimize retrieval for each tissue and antibody.
Section 2
What Is the Expected CASR Staining Pattern?
CASR is a cell membrane receptor with seven transmembrane segments (UniProt P41180 topology). In tissue IHC, expect membranous and cytoplasmic staining in parathyroid glandular cells, pancreatic endocrine cells, and a subset of renal tubules, including distal tubules (HPA: tissue IHC profile; High in each listed cell type). HPA rates the tissue staining profile Enhanced, citing agreement with RNA expression and external characterization (HPA: reliability Enhanced).
| Strong cell-border staining, with some cytoplasmic signal, in parathyroid glandular cells, pancreatic endocrine cells, or distal renal tubules. | This matches the reported cellular distribution and High staining in those cell types (HPA: tissue IHC). Score the relevant cells and their compartment, rather than treating every cell in a positive organ as positive (HPA: cell-specific tissue IHC profile). |
| Predominantly nuclear staining, without a convincing cell-border or cytoplasmic pattern, in an otherwise positive tissue. | Treat this as a suspect compartment pattern: UniProt places CASR at the cell membrane, while HPA reports membranous and cytoplasmic tissue staining (UniProt P41180: subcellular location; HPA: tissue IHC profile). Review controls and detection background before assigning it to CASR (standard IHC practice). |
| Strong staining in cells reported as not detected, such as adipocytes in adipose tissue or adrenal glandular cells. | That conflicts with the listed HPA cell-level results (HPA: Not detected in adipose adipocytes and adrenal glandular cells). Consider cross-reactivity or endogenous detection activity; compare a matched negative control and the expected positive cells (standard IHC practice). |
| Broad, hazy chromogen across unrelated cells or the section, with poorly defined cell borders. | A diffuse pattern cannot be read as the reported cell-specific CASR pattern (HPA: tissue IHC profile). Check background with an appropriate negative control, then review blocking, washes, and detection chemistry (standard IHC practice). |
| No staining in parathyroid glandular cells, pancreatic endocrine cells, or distal renal tubules. | Each is reported as High by HPA, so a blank known-positive control calls for an assay check (HPA: tissue IHC). Confirm tissue identity and control performance, then review retrieval, antibody conditions, and detection according to the validated IHC workflow (standard IHC practice). |
💡Expected CASR appearanceCall the stain positive when High membranous and cytoplasmic signal marks the specified glandular, endocrine, or distal tubular cells (HPA: tissue IHC); isolated nuclear or widespread cell-independent color is suspect against that pattern (UniProt P41180: cell membrane; HPA: tissue IHC profile).
| Which tissues and cells provide the clearest comparison? | Parathyroid glandular cells, pancreatic endocrine cells, and kidney distal tubules are listed as High; duodenal glandular cells are Low (HPA: tissue IHC). Use cell-level comparisons because a whole organ can contain both expected and uninformative cells (HPA: cell-specific profile). |
| What does receptor topology contribute? | CASR has an extracellular region at residues 20–610, seven membrane segments, and a cytoplasmic region at 855–1078 (UniProt P41180 topology). Those regions make epitope location relevant when assessing compartment staining; the supplied HPA antibody entries do not identify their epitopes (HPA: antibody entries). |
| Can the listed antibodies support the tissue pattern? | Both HPA039686 and HPA050335 carry Enhanced IHC status (HPA: antibody validation). The reported profile also has Enhanced reliability from agreement with RNA expression and external characterization (HPA: reliability description). These ratings support the stated tissue pattern, without establishing performance under every local staining condition. |
| Can this result be applied to IF/ICC? | Use the membrane location as a localization expectation (UniProt P41180: cell membrane; HPA: subcellular summary Membrane). HPA lists no ICC-IF image cell lines and no ICC validation status for these antibodies (HPA: subcellular and antibody entries), so this record does not establish an IF/ICC staining result or an IF protocol. |
| Do processing or isoforms change the call? | UniProt lists a signal peptide at residues 1–19, a mature chain at 20–1078, and two isoforms (UniProt P41180: processing; isoforms). Without a supplied antibody epitope or isoform-specific staining record, these annotations cannot justify a different tissue pattern or explain a negative slide (HPA: antibody entries). |
| Situation | Likely cause | Next action |
|---|---|---|
| Expected positive cells are blank, while the section appears intact. | The result conflicts with High staining reported in parathyroid glandular cells, pancreatic endocrine cells, and distal tubules (HPA: tissue IHC). The supplied sources do not identify a CASR-specific fixation sensitivity. | Verify tissue and cell identity; run a known-positive control and review the validated IHC antibody, retrieval, and detection settings (standard IHC practice). Do not attribute the failure to a CASR-specific fixation effect without separate evidence. |
| Only nuclei stain in a nominally positive tissue. | Nuclear-only staining does not fit the membrane location or HPA's membranous and cytoplasmic tissue profile (UniProt P41180: subcellular location; HPA: tissue IHC profile). | Compare the same run with a known-positive section and a negative detection control; inspect whether nuclear color persists without primary antibody (standard IHC practice). |
| Most cell types show equally strong color, including listed negative cells. | A uniform pattern conflicts with HPA's cell-specific positives and Not detected entries (HPA: tissue IHC). Cross-reactivity or endogenous detection activity are possible explanations (standard IHC practice). | Include a no-primary control and inspect detection reagent background; optimize blocking, washes, and detection conditions according to the assay workflow (standard IHC practice). |
| Kidney has signal, but the stained structures are unclear. | HPA reports High staining in distal tubules and describes expression in a subset of renal tubules, so an organ-wide positive label loses the reported cell specificity (HPA: tissue IHC). | Identify the renal structures on the counterstained section before scoring and record staining by tubule type and compartment (standard IHC practice; HPA: distal tubules High). |
| Parathyroid and pancreatic sections differ in overall apparent signal. | HPA reports High staining in glandular and endocrine cells, respectively, rather than identical staining across every cell in each section (HPA: tissue IHC). | Compare the specified positive cells at similar staining exposure and score their membranous and cytoplasmic pattern; avoid comparing whole-section darkness alone (HPA: tissue IHC profile; standard IHC practice). |
| An IF/ICC image is diffuse or seems inconsistent with the IHC slide. | HPA's IF-related summary says Membrane, but supplies no ICC-IF image cell lines or ICC status for the listed antibodies (HPA: subcellular and antibody entries). Tissue IHC validation does not itself document IF/ICC performance. | Treat the IF/ICC image as a separate assay result and assess its controls and cellular localization independently; use this page's tissue IHC pattern only as context (HPA: tissue IHC; standard IF practice). |
Experiment evidence
IHC & IF images showing CASR staining
PB9924 · IHCIHC analysis of CASR using anti-CASR antibody (PB9924). CASR was detected in a paraffin-embedded section of mouse kidney tissue. Heat mediat
PB9924 · IHCIHC analysis of CASR using anti-CASR antibody (PB9924). CASR was detected in a paraffin-embedded section of rat kidney tissue. Heat mediated
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000036828-CASR/tissue/cerebral+cortex#imid_20354063
HPA · Parathyroid glandHuman Protein Atlas IHC, Parathyroid gland. Source: https://www.proteinatlas.org/ENSG00000036828-CASR/tissue/parathyroid+gland#imid_20360784
HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000036828-CASR/tissue/colon#imid_20360819
HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000036828-CASR/tissue/liver#imid_20360828
← swipe / scroll for more images →
Real IHC / IF data behind the staining-pattern expectations in this section.
Sample controls for CASR IHC & IF
🧪Run kidney first and expect staining in distal tubules (HPA: kidney distal tubules High). Use adipose tissue as a negative tissue, focusing on adipocytes (HPA: adipocytes Not detected); on the kidney slide, unstained cells outside distal tubules can serve as background comparators, but HPA does not identify them as CASR-negative (HPA: kidney distal tubules High).
Positive control tissue: Kidney (Distal tubules, HPA High)
Negative control tissue: Adipose tissue (HPA Not detected)
ICC-IF cell lines (HPA subcellular resource): HPA carries no ICC-IF cell line for CASR; derive a cell-line control from the positive tissue's cell type (Distal tubules) and confirm it by RNA or western blot first.
Technical controls: Include a no-primary, secondary-only control, a host-matched rabbit IgG isotype control, and CASR-knockout tissue if available (PB9924 caption: rabbit primary; standard IHC controls). For kidney sections, quench endogenous peroxidase and check for endogenous biotin background with the biotin-based DAB detection system (PB9924 caption: mouse kidney, biotinylated secondary and SABC/DAB; standard IHC practice).
⚠️Feasibility: A target-specific fixation window or fixation effect is unreported, and the selected PB9924 paraffin-section caption does not state a fixative (PB9924 caption: fixative not stated). Start retrieval optimization from the reported heat-mediated EDTA protocol at pH 8.0; the caption used 1 μg/ml primary overnight at 4°C (PB9924 caption). Whether frozen sections or IF are easier is unreported (PB9924 caption: paraffin IHC; HPA subcellular: no ICC-IF image cell lines); endogenous biotin can complicate kidney staining with this detection system (PB9924 caption: kidney and SABC/DAB; standard IHC practice).
HPA tissue IHC evidence for CASR
Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Enhanced — High consistency between antibody staining and RNA expression data. External characterization data supports antibody staining.). 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 |
|---|---|---|---|---|
| Kidney | Distal tubules | High | Protein (IHC) | HPA → |
| Pancreas | Pancreatic endocrine cells | High | Protein (IHC) | HPA → |
| Parathyroid gland | Glandular cells | High | Protein (IHC) | HPA → |
Undetected expression · recommended negative controls
| Tissue | Cell type | Level | Evidence | Source |
|---|---|---|---|---|
| Adipose tissue | Adipocytes | Not detected | Protein (IHC) | HPA → |
| Adrenal gland | Glandular cells | Not detected | Protein (IHC) | HPA → |
| Appendix | Glandular cells | Not detected | Protein (IHC) | HPA → |
| Bone marrow | Hematopoietic cells | Not detected | Protein (IHC) | HPA → |
| Breast | Adipocytes | Not detected | Protein (IHC) | HPA → |
Section 3
Advanced CASR IHC Tips
Troubleshoot CASR staining in paraffin sections by checking retrieval, cell type, subcellular pattern, and controls before comparing signal intensity.
Where should I start if CASR staining is weak in paraffin sections?
Start with heat-mediated retrieval in EDTA at pH 8.0 for PB9924 paraffin-section IHC (datasheet PB9924). The selected mouse kidney example used this retrieval before 10% goat-serum blocking and 1 μg/ml primary antibody overnight at 4°C (datasheet PB9924). If staining is weak, compare retrieval duration across adjacent sections while holding antibody concentration and chromogen development constant (standard IHC practice). Include a renal-tubule reference section in each run, because CASR staining occurs in a subset of renal tubules and is high in distal tubules (HPA tissue IHC). Record both signal and tissue damage before choosing the retrieval condition (standard IHC practice).
Can the kidney image tell me which fixation conditions preserve CASR staining?
No target-specific fixation sensitivity is established by the supplied evidence: the PB9924 kidney caption describes a paraffin section but does not state its fixative (datasheet PB9924). Record fixative, fixation duration, processing history, and section age for each specimen before comparing staining (standard IHC practice). Use similarly processed positive and negative controls, then keep the documented EDTA pH 8.0 retrieval and 1 μg/ml overnight primary incubation constant during a fixation comparison (datasheet PB9924; standard IHC practice). If a fixation group stains weakly, assess tissue morphology and controls before attributing that result to CASR antigen loss (standard IHC practice).
Should CASR appear only at the cell surface in kidney IHC?
Expect a membrane-associated pattern because CASR is annotated at the cell membrane and has 7 transmembrane segments (UniProt P41180 topology and subcellular location). Cytoplasmic staining is also reported alongside membranous staining in a subset of renal tubules, pancreatic islets, and parathyroid gland (HPA tissue IHC). In kidney sections, judge both compartments within identified tubules rather than scoring diffuse whole-section DAB as receptor staining (HPA tissue IHC; standard IHC practice). Compare the distribution with high CASR staining in distal tubules, and document membrane and cytoplasmic scores separately when the pattern varies among cells (HPA tissue IHC; standard IHC practice).
How can epitope position change the CASR staining pattern?
CASR has 2 annotated isoforms, but the supplied PB9924 caption does not identify the antibody epitope or establish isoform selectivity (UniProt P41180 isoforms; datasheet PB9924). Its large extracellular region spans residues 20–610, while the cytoplasmic tail spans 855–1078 (UniProt P41180 topology). The record lists 11 glycosylation sites in the extracellular region and phosphorylation sites in the tail; these annotations do not establish how either feature affects this antibody's staining (UniProt P41180 modifications). Obtain the epitope documentation before interpreting differential staining as an isoform difference, and keep retrieval conditions matched when comparing specimens (standard IHC practice).
How should I investigate CASR localisation by multiplex IF?
For an IF pilot, pair CASR with a validated marker of the expected cell type; distal tubules are a useful kidney reference because they show high CASR staining in tissue IHC (HPA tissue IHC; standard IF practice). Choose spectrally separated fluorophores and test a far-red channel against tissue autofluorescence using unstained sections (standard IF practice). Decide on permeabilisation only after establishing the antibody epitope: an extracellular epitope and a cytoplasmic-tail epitope have different access requirements (UniProt P41180 topology; standard IF practice). The supplied PB9924 example documents paraffin-section chromogenic IHC, so verify IF staining and controls independently before treating its pattern as confirmed in IF (datasheet PB9924; standard IF practice).
What should I check when kidney sections show widespread brown signal?
First inspect a no-primary control and a matched positive section to separate detection-system background from CASR staining (standard IHC practice). The PB9924 example uses a biotinylated secondary, streptavidin–biotin detection, and DAB, so check endogenous biotin and peroxidase activity and apply the corresponding blocks where needed (datasheet PB9924; standard IHC practice). The example used 10% goat serum for blocking and 1 μg/ml primary antibody overnight at 4°C; reproduce those documented conditions before changing one variable at a time (datasheet PB9924). Evaluate background against the reported subset-of-tubules pattern rather than assuming every stained kidney cell is positive (HPA tissue IHC).
How should I score variable CASR staining across kidney tubules? ⚠ ANSWER MARKED FOR VERIFICATION
Define the renal-tubule population and score viable cells within it, because HPA reports staining in a subset of renal tubules and high staining in distal tubules (HPA tissue IHC). For intensity-weighted scoring, use an H-score of 0–300: sum each intensity grade from 0–3 multiplied by its percentage of cells (standard IHC practice). Report membrane and cytoplasmic H-scores separately, or report the percentage of positive cells with the threshold fixed before scoring (HPA tissue IHC; standard IHC practice). Normalize each percentage to the number of eligible tubule cells, and any stained-area density to measured viable tissue area in mm² (standard IHC practice).
When is an apparent CASR-positive cell likely to be an artefact?
Give greatest weight to staining in the expected cells and compartments: CASR is a cell-membrane receptor, while HPA reports membranous and cytoplasmic staining in selected renal tubules (UniProt P41180 subcellular location; HPA tissue IHC). Question uniform staining across unrelated cells, signal confined to section edges, and deposits over necrotic areas; compare each with intact internal tissue (standard IHC practice). With the documented biotin-based DAB workflow, check no-primary and detection controls before calling widespread brown signal CASR-positive (datasheet PB9924; standard IHC practice). A convincing result should reproduce the cell-type pattern across comparable sections under the same retrieval and development conditions (HPA tissue IHC; standard IHC practice).
Boster reagents
Best CASR / Extracellular calcium-sensing receptor IHC Antibodies
PB9924 is an IHC-validated anti-CASR antibody for paraffin sections, with mouse and rat kidney images (PB9924 image captions); its listed reactivity also includes human (catalog: PB9924).
Real IHC data
Anti-Calcium Sensing Receptor/CASR Antibody ®
Cat # PB9924
PB9924 is the only SKU shown and lists IHC as an application for human, mouse and rat samples (catalog: PB9924). Its IHC images show staining in paraffin-embedded mouse and rat kidney sections (PB9924 image captions).
Which to pick: Choose PB9924 for paraffin-section IHC; its captions document heat retrieval in EDTA at pH 8.0, and the fixative is unreported (PB9924 image captions). For cross-species work, PB9924 lists human, mouse and rat reactivity, with IHC images for mouse and rat only (catalog: PB9924; PB9924 image captions). No IF/ICC-validated SKU is supplied, so there is no supported IF/ICC pick here (catalog: PB9924 applications).
Each figure is that product's own IHC / IF validation image from its datasheet.
References
- UniProt Consortium. UniProt entry P41180 (CASR_HUMAN, Extracellular calcium-sensing receptor).
- Human Protein Atlas. CASR tissue IHC expression (reliability: Enhanced).
- Human Protein Atlas. CASR subcellular location (ICC-IF): Membrane.
- Human Protein Atlas. CASR antibody validation summary (2 antibodies).
- Differential parathyroid and kidney Ca(2+)-sensing receptor activation in autosomal dominant hypocalcemia 1. EBioMedicine 2022 — PMC8935519.
- Expression of calcium sensing receptor and E-cadherin correlated with survival of lung adenocarcinoma. Thoracic cancer 2015 — PMC4632928.
- The suppressive role of calcium sensing receptor in endometrial cancer. Scientific reports 2018 — PMC5773571.
- Calcium Sensing Receptor Inhibits Growth of Human Lung Adenocarcinoma Possibly via the GSK3β/Cyclin D1 Pathway. Frontiers in cell and developmental biology 2020 — PMC7330125.
- PubMed PMID:8813042 — UniProt-cited evidence.
- PubMed PMID:7759551 — UniProt-cited evidence.
- PubMed PMID:7677761 — UniProt-cited evidence.
Immunohistochemistry protocol sheet for CASR (Extracellular calcium-sensing receptor). Expected localisation Membranous and cytoplasmic staining (HPA tissue IHC). Antigen retrieval: EDTA pH 8.0 HIER, heat-mediated (datasheet PB9924). Validated IHC antibody: PB9924 at 0.5-1μg/ml (the product's own IHC validation image is shown). Controls (HPA): positive Kidney (Distal tubules); negative Adipose tissue. IHC-P workflow on paraffin sections; fixative unspecified. Protocol steps: 1. Sample: Paraffin-embedded mouse kidney tissue; fixative not specified (datasheet PB9924); 2. Fixation: Image fixative and duration unreported (datasheet PB9924); verify before use.; 3. Sectioning: 4–5 µm sections on charged slides (standard); 4. Deparaffinisation: Xylene, graded ethanol series to water (standard); 5. Antigen retrieval: Heat retrieval: EDTA pH 8.0 (datasheet PB9924); 20 min, 95–100 °C (standard); 6. Peroxidase block: 3% H2O2, 10 min , room temperature (standard); 7. Blocking: 10% goat serum (datasheet PB9924); 8. Primary antibody: Rabbit anti-CASR, 0.5-1μg/ml (datasheet PB9924); 9. Primary incubation: Overnight at 4 °C (datasheet PB9924). Watch for: Fixation: Keep fixation consistent across sections (standard IHC practice; not target-specific); Matched tissue-IHC evidence does not establish the fixation claim. Validate the specimen-specific method before use. (selected-SKU IHC image PB9924); Caveat: Only a subset of renal tubules stains (HPA tissue IHC); Isoform / epitope: 2 isoforms; check whether the epitope is extracellular or cytoplasmic (UniProt); Regulation: Expression regulation is unreported (UniProt). Evidence: UniProt P41180, HPA tissue IHC · Enhanced, HPA ICC-IF · Membrane, Datasheet PB9924, PMC8935519, PMC4632928. QR code links to https://www.bosterbio.com/bosterbio-gene-info-cards/CASR/immunohistochemistry-ihc-guide.