Acute Effects on Metabolic Blood and Tissue Parameters in Anesthetized Rats

Acute Effects on Metabolic Blood and Tissue Parameters in Anesthetized Rats 

Anesthetized rats are used for testing the side effect potential of a candidate compound on intermediary metabolism in liver, muscle and adipose tissue with subsequent effects on metabolic blood parameters (e.g. glucose, lactate, free fatty acids, triglycerides) and insulin. The use of anesthetized rats represents more a principal assessment of the pharmacological side effect potential since the candidate compound must be administered intravenously or intraperitoneally (enteral/intestinal administration should be avoided due to the anesthesia-induced decrease in intestinal motility with subsequent impairment of enteral absorption), compared to the study in conscious rats in which the candidate compound can be studied after oral administration, which in most cases represents the clinical route of administration for small molecular drugs. 

Metabolic blood parameters are assayed in anesthetized male rats using a modified method of glucose clamp studies in rodents (Terrettaz and Jeanrenaud 1983). Four to 6 rats per group (vehicle control and one dose of the candidate compound) are used. Rats are anesthetized with an intraperitoneal injection of pentobarbital sodium (60 mg/kg), tracheotomized, and one jugular vein per rat is cannulated for intravenous infusion the other vein is prepared for collection of blood samples. Anesthesia is maintained for up to 7 hours by subcutaneous infusion of pentobarbital sodium (adjusted to the anesthetic depth of the individual animal about 24 mg/kg/h). Body temperature is monitored with a rectal probe thermometer, and temperature is maintained at 37 °C by means of a heated surgical table. Blood samples for glucose analysis (10 il) are obtained from the tip of the tail every 15 minutes, and for lactate analysis (20 p.1) every 

30 minutes. The rats are allowed to stabilize their blood glucose levels after surgery for up to 2 hours. Then, the candidate compound is injected or infused intravenously or administered intraperitoneally, respectively. Blood samples (100 p.1) for detection of free fatty acids, triglycerides and insulin are collected from a peripheral vein (e.g. jugular vein) immediately prior and every 1 or 2 hours after compound administration. 

The differences of the metabolic blood parameters after compound administration are calculated with respect to the pre-drug values and against a control group, which has received the vehicle only. The metabolic tissue parameters at the end of the study are assessed between control and treatment group. 

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