BU IACUCInstitutional Animal Care and Use Committee IACUC oversee... approved May 2009, Revised January 2014, Revised July 2019

Boston University is committed to observing federal guidelines and AAALAC international guidelines for the humane care and use of animals.

This policy deals with ionizing irradiation of mice and rats exposed to gamma irradiation emanating from a 137cesium source. Experimental reasons for exposing rodents to ionizing radiation are used in the fields of immunology and cancer biology. Irradiation to produce myeloablation preparatory to bone marrow transplantation (BMT) is frequently used. BMT procedures are addressed elsewhere in a separate IACUC policy.



Doses of Irradiation

There are numerous literature references reporting differences in sensitivity in radioresistance or radio susceptibility to radiation damage in different strains of mice. If the PI is unfamiliar with the strain to be used or the radiation source, it is advisable to irradiate a small number of animals in a pilot study to determine to optimal dose for the project and strain under study. The age of the mouse is important as well, older mice being more resistant. For myeloablation in preparation for BMT, total whole-body irradiation (TBI) is used. Doses of 700 to 1300 cGy are myeloablative 2 (Duran-Struuck, R. and Dysko, R., 2009). Mice of the C57BL strain are more resistant to irradiation damage, whereas BALB/c mice are more sensitive.

Table 1
Published doses of irradiation for various rat and mouse stocks and strains
(2X indicates fractionated doses are given three hours apart)

Mouse StrainProtocolDose (Gy)Response to DoseReference
C57BLTBI and
2X 5.5SurvivalThe Mouse in Biomedical Research. Vol 3. Fox J.G et. Al. Eds. 2nd Ed. 2007. Academic Press. ACLAM Series. P. 453.
C57BLHematopoietic ablation3.5–6.0
2X 5.5 G
Source: 60Co irradiator
0.8 Gy
1.4 Gy
The F1 hybrid is similar in radiosensitivity to the C57BL/6 and different from the BALB/cHanson et. al. 1987. Comparison of intestine and bone marrow radio sensitivity of the BALB/c and the C57BL/6 mouse strains and their B6CF1 offspring. Radiat Res 110:340–352.


TBI and BMTSource 137Cs
10–22 Gy
Germ-free (GF) mice were much less sensitive to radiation enteritis than conventional miceCrawford, PA and Gordon, JI Microbial regulation of intestinal radiosensitivity. PNAS 102(37); Sept. 13, 2005.



Source 137Cs10 – 60 Gy10 – 50 Gy10 – 50 GySkin sensitivity Long-term damage
Mild damage Less sensitive than A/J
Severe skin damage
Severe skin damage
Iwakawa, M. et. al. 2003. Different radiation susceptibility among five strains of mice detected by skin reaction. J Radiat Res (Tokyo) 44: 7–13.
C57BL/6NCrB6.Cg-Ptpcrca/NCr(Ly5.2)TBI and BMTMore sensitive and more prone to bacteremia Less sensitiveDuran-Struuck, R. et.al. 2008. Differential susceptibility of C57BL/6NCr and B6.Cg-Ptprca mice to commensal bacteria after whole-body irradiation in translational bone marrow transplantation studies. J Transl Med: 6:10
Rat StockProtocolDose (Gy)Response to DoseReference
Wistar rats M 100gTBI14.4 GyIncreased serum Corticosterone 60 minutes and 3 days after exposure. Rats began to die on day 5 post-exposure.Kassayova, E. et.al. 1999. Two-Phase Response of Rat Pineal melatonin to Lethal Whole-Body Irradiation with Gamma Rays. Physiol. Res. 48:227–230.
Wistar rats M 100gTBI9.6 GyRats began to die on day 10 post-exposure.Same
Wistar rats M 100gTBI4.8 GySame








Care of Irradiated Mice








Humane Endpoints for Irradiated Mice

In the case of BMR, transplanted mice undergo a 5–10 day irradiation sickness period from which they generally recover within 14 days (Duran-Struuck, R and Dysko, R., 2009). Depending upon radiation dose, they may lose as much as 25% of their body weight by day seven, but if successfully reconstituted will regain most of this weight during the following week. If mice have not received a bone marrow transplant they will remain sick and/or die, the time of death depending upon the dose.

  • If animals are not well on their way to recovery by day 14, considerations should be given to euthanasia. Consultation with veterinary staff is highly recommended. Moribund animals must be euthanized.
  • If not recovered by day 21 post-irradiation, animals must be euthanized.


Gamma irradiation: one type of ionizing irradiation. The source may be 137cesium, 60cobalt, or high-energy X-rays. This policy refers to the 137cesium irradiator at BUMCBoston University Medical Campus.

Gray (Gy): the SI unit of absorbed radiation dose due to ionizing radiation.

Rad: a largely obsolete unit of absorbed radiation dose. It is now superseded in the SI by the “gray”. 100 rads = 1 gray (Gy).

Fractionation of dose: The total irradiation dose is split into two or more equal parts separated by a time interval in order to minimize morbidity and mortality.

BU ASC Sulfatrim (SEPTRA) Doses and Dilutions

Revised April 2008

SulfaTrim stock solution (oral suspension):

200mg Sulfamethoxazole and 40mg Trimethoprim/5ml = 240mg SulfaTrim/5ml

Mouse drinks 15ml/100g/24 hours = 150ml/kg/24 hours

Rat drinks 10ml/kg/24 hours = 100ml/kg/24 hours