Evaluation of a surgical procedure to measure drug biliary excretion of rats in regulatory safety studies

Abstract

A surgical procedure was evaluated to allow bile collection from the freely moving male Sprague-Dawley rats for the assessment of drug biliary excretion during regulatory safety studies. A catheter was implanted into the bile duct to divert the bile flow via an exteriorized loop. Following recovery from the surgery and verification of normal hepatic function, the exteriorized catheter was sectioned to allow collection of the bile and replacement with a commercial bile salt solution. Approximately 80% of the catheterized animals (10 females and 10 males) had normal serum liver enzyme levels 2 days after surgery. Then, the effect of acute or repeated administrations of the immunosuppressant tacrolimus on the biliary excretion of 14C diazepam was studied to validate the technique. A first group of 12 rats received an intravenous injection of 10 mg/kg 14C-diazepam and the total and sequential amounts of diazepam excreted in the bile were measured over 72 h. Biliary excretion accounted for 80% of diazepam elimination. These rats were then given an oral administration of 3 mg/kg tacrolimus on days 7 and 8 followed by the same intravenous dose of 14C-diazepam. Another group of 10 catheterized rats was given 21 daily oral doses of 3 mg/kg tacrolimus followed by a single intravenous administration of 14C-diazepam. No significant changes in diazepam biliary excretion were observed following either acute or repeated administration of tacrolimus. This study demonstrates the feasibility of drug biliary excretion investigations under Good Laboratory Practices conditions as a complement to regulatory acute or repeated dose safety studies.

An updated and simplified method for bile duct cannulation of rats

“…5,6 The loss of BW in groups A and B did not reach statistical significance at any time point and was regained 4 -5 days after surgery, which is consistent with BW loss previously reported in BDC rats. 6,11 Surgery has a debilitating effect 11,13 and weight loss was most likely due to surgery-related stress rather than the specific surgical procedure, as demonstrated by the similarity between groups A and B. This means that the simplification of the BDC method did not compromise the wellbeing of the animals more than a simple laparotomy.…”

“…18 Postoperative variations in clinical biochemistry parameters were described by van Wijk et al 11 who noted them to be outside normal limits in rats following surgery. Also, Faure et al 13 reported enzyme and total bilirubin parameters outside the normal range on day two in 15 -65% of rats following surgery, but approximately half of these animals regained normal values eight days postsurgery. Furthermore, deviations in liver enzymes have been reported by West et al 19 in BDC rabbits.…”

“…6 Variations include exteriorization of the catheter through the neck, 7 skull, 8 flank 9,10 or tail 11 of unrestrained conscious animals. 12,13 The present study describes a simplified and refined modification of the unrestrained freely moving single BDC rat model for short-term studies. 5,14 Blood sampling in this model makes it feasible for intestinal absorption studies.…”

Mass Balance Studies in Animals and Humans

“…The animal is then placed back to metabolic cage and externalized tubing is attached to a dual channel swivel. The bile flow needs to be closely monitored for 1-2 h before the studies [30], and if possible, liver function tests can be performed by monitoring the level of alanine aminotransferase (ALT), aspartate aminotransferase (AST), and bilirubin [31]. Control bile is collected from the bile-duct cannula up to 0.5 h pre dose.…”

Recommendation to Exclude Bile-Duct-Cannulated Rats with Hyperbilirubinemia for Proper Conduct of Biliary Drug Excretion Studies

“…An extracorporeal BDC bypass loop is implanted into the rats by surgery (Lipsky and Berkley, 1977) to collect bile specimens from the animals under unrestrained freely moving conditions (Balabaud et al, 1981). However, the BDC surgery sometimes causes hyperbilirubinemia (HB) (Faure et al, 2006). Decreased hepatobiliary transport of bilirubin and its glucuronides is a possible cause of the HB in such rats.…”