SOP 10.17 Acute DSS Colitis (Rat Model)

1. Introduction and Definitions:

Dextran sodium sulfate (DSS) is a molecule that induces colitis like that seen in human patients. It is administered to the animal via their drinking water. This is a common model of Inflammatory Bowel Disease (IBD), the condition of chronic intestinal inflammation that is currently incurable. 

Optimal DSS concentrations are determined by preliminary experiments, as disease severity often varies dependent on animal age, gender, and strain. Standard drinking water is given to controls.

2. Materials:

• Water bottle
• DSS solution
• Lactated Ringer’s solution
• 1-5ml sterile syringes
• Sterile needles(26-27gauge)
• Alcohol swabs
• Weight scale

3. Procedures

• Prior to the initiation of a DSS cycle, all study rats must be weighed to obtain a baseline weight and it is recorded with the date on the cage card. Based on the baseline weight, the 5%, 10% and 15% weight loss value are calculated.
• DSS is dissolved into standard drinking water to yield the desired concentration (2.5%-5%) (“%” = g/100mL). 
• Regular water bottles are removed from the cages and replaced with the DSS dosed bottles. 
• DSS is administered in drinking water for 5 days, followed by a return to regular water. 
• Non-standard water bottles are used for the DSS rats, and a special request is required for them. Special requests must be submitted to ACS. 

Monitoring:

• Ensure that cages are flagged with specific ACS cage alerts that animals are on a DSS study. 
• Daily monitoring: cages are checked for DSS water consumption (volume drop in bottle, urine output) and bottles are topped up as necessary. 
• Daily weight, appearance, and behavioural changes must be recorded at room level. 
• All rats in a DSS treated group must receive a daily subcutaneous injection of 5mL Lactated Ringer’s Solution (LRS). Every animal requires a new sterile syringe and needle, refer to SOP 10.9 “Injection Techniques in Rats”. Rats must be weighed before fluid therapy administered. 

Clinical Outcomes:

• Treated rats may develop loose stool or diarrhea with detectable blood in stool. 
• Rats show ruffled fur and weight loss while the colitis is present. 
• Weight loss should not reach a 15% decrease from baseline value, unless approved within the Animal Use Protocol. 
• All humane endpoints as approved in the Animal Use Protocol must be followed.