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The rat CTR (calcitonin receptor) is encoded by the *Calcr* gene and belongs to the Class B G protein-coupled receptor family. It is expressed in both the central nervous system (e.g., the nucleus accumbens and the nucleus of the solitary tract) and peripheral tissues (e.g., the kidney and mammary gland). Rat CTR exists as two isoforms, C1a and C1b; C1a exhibits high affinity for salmon calcitonin but low affinity for human/rat calcitonin, whereas C1b displays even lower ligand affinity due to a 37-amino-acid insertion in its extracellular domain. Additionally, CTR can form a functional amylin receptor when co-expressed with RAMP proteins, and it serves as an important marker for osteoclasts.

The CHO-K1 Rat CTR CRE-Luc Cell Line model effectively simulates the in vivo Rat CTR signal transduction process.

Figure 1. Dose Response of Agonists in Rat CTR CRE-Luc CHO(C20) .


Figure 2. HTRF cAMP Assay with Rat CTR CRE-Luc CHO(C20) .

Cell Resuscitation
1)Rapidly thaw the frozen cells in a 37 °C water bath for approximately 60 seconds. Once thawed (which may take slightly less or more than 60 seconds), immediately transfer the cell suspension from the cryovial into a 15 mL centrifuge tube containing 10 mL of pre-warmed CHO-K1 Rat CTR CRE-Luc Cell Line complete culture medium.
2)Centrifuge cells at 1000 rpm for 5 min to remove medium, then resuspend cells in 5 mL of pre-warmed complete medium.
3)Transfer the cell suspension into a T25 culture flask and incubate at 37 °C with 5% CO₂.
4)After approximately 24–36 hours, replace the medium or passage the cells to remove non-adherent dead cells.

Subculturing procedure
1)When the cell density reaches the appropriate confluency for passaging, wash the cells with PBS, then add 1 mL trypsin to detach the cells. When more than 80% of the cells detach upon gently tapping the culture flask, add complete culture medium to terminate digestion. Gently pipette to obtain a single-cell suspension, transfer to a 15 mL centrifuge tube, and centrifuge at 1000 rpm for 5 minutes.

2)Discard supernatant after centrifugation. Resuspend cells in fresh medium to a single-cell suspension and transfer to a new culture flask for continued growth.

Cell Freezing
After trypsinization and centrifugation of cells from each T75 flask or 10 cm culture dish, discard the supernatant. Add 2 mL of cryopreservation medium (90% FBS + 10% DMSO), gently resuspend thoroughly, and aliquot into two cryovials. Immediately place the cryovials into a controlled-rate freezing container (e.g., Nalgene 5100-0001), fill with isopropanol to the indicated level, and store at −80 °C. After 24 hours, transfer the cryovials to liquid nitrogen for long-term storage.