Rabbit Hepatocytes, Suspension

Species specificity of BA-CoA conjugate formation

Para-substituted benzoic acids (p-BA) and their metabolites are known to impair sperm quality in male rats, potentially linked to p-BA metabolism into toxic intermediates. To further investigate the role of p-alkyl-benzoyl-CoA accumulation in male reproductive toxicity in rats and rabbits, and to examine its species specificity.

In rabbit hepatocytes, initial formation of p-tBBA-CoA and p-iPBA-CoA was observed for BMHCA and PMHCA, respectively. However, unlike in rat hepatocytes, these conjugates decreased over 22 hours, with levels becoming nearly undetectable at lower doses (Fig. 1). For example, after 22 h exposure to 50 µM BMHCA, p-tBBA-CoA in rabbit hepatocytes was 0.09 µM-about 20-fold lower than in rat hepatocytes (1.99 µM). The kinetic profile in rabbits resembled that of non-reprotoxic aldehydes in rats (Fig. 2). Higher initial CoA levels occurred with direct benzoic acid exposure versus parent aldehydes, as aldehydes require prior metabolism. A similar declining kinetic profile was seen for benzoic acids in rabbits, distinct from rats.

In human hepatocytes exposed to BMHCA, initial p-tBBA-CoA levels were much lower than in rats and decreased rapidly to near the detection limit by 22 h (Fig. 1). For PMHCA, p-iPBA-CoA levels in human hepatocytes were lower than in rat hepatocytes, and they declined over time similarly to rabbit hepatocytes. As in rabbits, direct benzoic acid exposure led to higher initial conjugate levels than aldehyde exposure, but conjugates still decreased rapidly. Overall, the CoA conjugation kinetics in human hepatocytes resembled the profile of non-reprotoxic compounds in rats.