No obvious toxicological influences of 50 µL microsampling from rats administered phenacetin as a drug with hematological toxicity.

According to ICH S3A Q&A focusing on microsampling, its application should be avoided in main study animals for test drugs that could exacerbate hematological parameters with frequent blood sampling. However, no study has reported the effects of microsampling on toxicity parameters of drugs known to induce hematological toxicity. Therefore, we assessed the toxicological effects of serial microsampling on rats treated with phenacetin as a model drug. In a common 28-day study, 50 µL of microsampling was performed at 6-time points on days 1 to 2 and 7-time points on days 27 to 28 from the jugular vein of Sprague Dawley rats. The study was performed independently by two organizations. The toxicological influence of microsampling was evaluated on body weight, food consumption, hematology, blood clinical chemistry, urine parameters, organ weights, and tissue pathology. Phenacetin treatments induced significant changes of various hematological parameters (including hemoglobin and reticulocytes), some organ weights (including liver and spleen), and some hematology-related pathological parameters in the liver, spleen and bone marrow. Meanwhile, serial microsampling exhibited minimal influence on the assessed parameters, although 20 parameters showed statistical differences mostly at one organization. The current results support the notion that serial 50 µL microsampling from the jugular vein had minimal impacts on overall toxicological profiles even in rats treated with a drug inducing hematological toxicity, but the potential adverse effect on certain parameters could not be fully excluded. Accordingly, this microsampling technique has possibility to be employed even for non-clinical rat toxicity studies using drugs with potentially hematological toxicity.

Lack of toxicological influences by microsampling (50 µL) from jugular vein of rats in a collaborative 28-day study.

Due to finalization of the ICH S3A Q&A focusing on microsampling, application of microsampling technique to regular non-clinical animal studies is expected for non-clinical safety assessment of pharmaceuticals. In Europe, microsampling from the tail vein or saphenous vein has often been used, whereas sampling from the jugular vein is thought to be more common for non-clinical studies in Japan. Therefore, we assessed the toxicological effects of serial microsampling from the jugular vein of SD rats in a common 28-day study at 4 independent organizations. Fifty microliter sampling was performed at 6 timepoints on day 1 to 2 and 7 timepoints on day 27 to 28 and its toxicological influences on body weight, food consumption, hematological and clinical chemistry parameters, and organ weights (on day 29 for 3 and day 28 for 1 organizations) were evaluated. The serial microsampling was shown to have no or minimal influences on the assessed parameters. The observed statistical differences for the 18 parameters were sporadic and did not appear to be systemically associated with microsampling. However, the sporadic changes were more often observed in females (14/18 parameters) than in males (6/18), suggesting the possibility that female rats were more susceptible to treatment-based influences. The current results indicate that serial 50 µL sampling from the jugular vein of SD rats had no or very slight toxicological effects, suggesting that this microsampling condition is applicable for toxicokinetic evaluation of non-clinical rat toxicity studies.

Various emetogens increase the secretion of salivary amylase in rats: a potential model in emesis research.

We investigated the effects of various emetic agents: cisplatin, apomorphine, lithium chloride (LiCl), rolipram, sibutramine, and the beta(3)-adrenoceptor (AR) agonist CL316243 on salivary amylase secretion in rats. We also determined the inhibitory effect of granisetron, a 5-HT(3)-receptor antagonist, on cisplatin-induced increased salivary amylase activity and the inhibitory effect of bilateral abdominal vagotomy on increases in salivary amylase activity induced by cisplatin and LiCl. Granisetron was administered 15 min before and 1 h after cisplatin administration. Cisplatin (10 - 15 mg/kg, i.v.) increased salivary amylase activity dose-dependently and induced an acute increase from 1.5 h post-treatment with 15 mg/kg. Apomorphine (1 - 3 mg/kg, s.c.), LiCl (120 mg/kg, i.p.), rolipram (3 - 10 mg/kg, p.o.), and sibutramine (10 mg/kg, p.o.) induced significant increases in salivary amylase secretion. On the other hand, CL316243 did not stimulate salivary amylase secretion. The increased amylase activity induced by cisplatin (15 mg/kg, i.v.) was inhibited significantly by granisetron (1 or 3 mg/kg x 2, i.v.) or tended to be inhibited by bilateral abdominal vagotomy, whereas an increase in amylase activity produced by LiCl was not inhibited by abdominal visceral nerve section. These results suggest that salivary amylase activity is useful as a marker for emesis in rats, a species that does not exhibit vomiting.