The Potential Influence of CO₂, as an Agent for Euthanasia, on the Pharmacokinetics of Basic Compounds in Rodents

Abstract

ABSTRACT:Rodent tissue distribution and pharmacokinetic studies were performed on basic compounds Org A and Org B in support of central nervous system drug discovery programs. A consistent observation from these studies was that drug concentrations in plasma obtained by cardiac puncture after CO 2 euthanasia were markedly higher compared with those from other sampling methods (serial sampling, isoflurane anesthesia, or cervical dislocation). Further investigations demonstrated that CO 2 euthanasia led to a reduction in blood pH in both rats and mice, which was not observed with the other sampling methods. The use of CO 2 euthanasia resulted in a decrease in the brain/plasma ratio of Org B, largely as a result of increased plasma concentrations. The pharmacokinetics of a basic drug, raloxifene, in rat were also influenced by sampling technique. CO 2 euthanasia before sampling, resulted in a 2-to 3-fold increase in the area under the drug concentration-time curve, a decrease in plasma clearance, and a decrease in the steady-state volume of distribution compared with isoflurane anesthesia. It is proposed that a decrease in the pH of blood relative to that of other tissues, as a consequence of CO 2 exposure, results in a redistribution of basic compounds out of the tissues, leading to higher concentrations in plasma.

The effect of Emdogain® and platelet-derived growth factor on the osteoinductive potential of hydroxyapatite tricalcium phosphate

“…The source of this material may be from a contaminant within the gelatin capsule or as a result of the fixation process. The formation of formalin pigment, also known as acid formaldehyde haematin, occurs due to the action of formaldehyde on haemoglobin at acid pH [54] resulting in a brown, intracellular and extracellular granular deposit. Although this is commonly associated with tissues that have been fixed in simple formalin fixatives such as 10% formalin or 10% formal saline, the formation of formalin pigment may have occurred with the use of neutral buffered formalin if the buffer was exhausted in the presence of an acidic blood and tissue pH following CO 2 inhalation euthanasia [55,56].…”

Lysosomal Sequestration (Trapping) of Lipophilic Amine (Cationic Amphiphilic) Drugs in Immortalized Human Hepatocytes (Fa2N-4 Cells)

“…In essence, lysosomes function as a drug reservoir and do not indefinitely trap xenobiotics. The rapid reversibility of lysosomal trapping of a lipophilic amine is shown by the effects of asphyxiating rats with carbon dioxide, which slightly acidifies the blood and causes a slight decrease in tissue levels and an increase in plasma drug levels (Angus et al, 2008). Although passive diffusion is one mechanism by which lipophilic amines can exit lysosomes, there are other mechanisms by which this can occur, namely mechanisms more relevant for the recycling of phospholipidbound drugs (Goldman et al, 2009).…”

Tissue and sex specificities in Ca2+ handling by isolated mitochondria in conditions avoiding the permeability transition

“…br/verificacao-autenticidade). Killing by decapitation was chosen because the use of anaesthetics or carbon dioxide could differentially bias the analyses of measured variables in an organ-specific manner (Brooks, 1999;Pecaut et al 2000;Angus et al 2008). Operation of the guillotine (rodent guillotine EB271; Insight, Ribeirão Preto, Brazil) was by the same trained and experienced laboratory assistant graduated in Sciences.…”