In risk assessment of chemicals, we often use default assessment factors to compensate for lack of knowledge. Such assessment factors can be especially useful for regulatory decisions. The present study focuses on assessment factors related to exposure duration, especially under sub-acute and sub-chronic conditions; and discussions attempt to utilize chemical-specific toxicological data. Most previous studies have not focused on target organs, but recent reports such as Malkiewicz et al. (2009) suggest that assessment factors may be target organ-dependent. Therefore, we addressed selected target organs (liver, kidney, blood, and body weight) by investigating assessment factors for these target organs. Using existing data, we calculated the ratio of the no-observed-effect level (NOEL) derived from sub-acute studies to the NOEL derived from sub-chronic studies, to assess for effects involving individual target organs (liver, kidney, blood, or body weight). Then, we compared these ratios with the ratio derived from the substances’ sub-acute and sub-chronic NOELs (the minimum values among all four target organs’ NOELs) by using the Dunnett’s multiple comparison test. Our analysis indicates that effects involving liver, kidney, and body weight need not be treated independently, although the effect on blood should be treated separately. Based on our results, we discuss potential refinement of assessment factors to reflect exposure duration.

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Philodryas nattereri is distributed in arid and semiarid regions of South America and is most common in northeastern Brazil. The aims of the work were to investigate the edematogenic and myotoxic effects promoted by P. nattereri venom. In this work, mice weighing 20-30 g (n = 4 for each experimental group) were used. For the edematogenic activity mice were injected in the subplantar region of the right foot pad with 50 µL of solutions containing different amounts of venom (3 and 10 µg) measured by plethysmometry at 0.5, 1, 2, 3, 6, 12 and 24 hr and pretreated with indomethacin, dexamethasone and antibothropic serum, whereas the left foot pad was injected with 50 µL of NaCl 0.15 M. Two hours after injection mice were killed by cervical dislocation and both feet were cut off and weighed individually. For the myotoxic activity mice were injected i.m. with 100 mL of solutions containing 50 µg of venom. Blood samples were extracted after 2, 4, 8, 12, 24 and 48 hr of venom injection to determinate serum CK activity and mice were sacrificed at the same time intervals to obtain the inoculated gastrocnemius muscle. They were fixed with formalin solution and stained with Hematoxylin-Eosin. Results showed that P. nattereri venom exhibits a high edematogenic and myotoxic activities. Myonecrosis reached its highest level after 2 hr of venom injection as shown by plasmatic CK levels (364 ± 92 U/L) and microscopic assay. It demonstrates the potential toxicity of the venom of P. nattereri, who inhabits the North-East region of Brazil.

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Philodryas nattereri is distributed in arid and semiarid regions of South America and is most common in northeastern Brazil. The aims of the work were to investigate the effects of the venom from P. nattereri in cultured of MDCK and RAW cells and abdominal writhes in mice. Based on oxidative metabolism, it was possible to observe that the venom was capable of significantly reducing cell viability only at higher concentrations of venom at 50 and 100 µg/mL for MDCK cells, while in 200 µg/mL to RAW cells, with an IC₅₀ of 169.5 µg/mL. Regarding writhing in mice promoted by the poison and acetic acid, it held a greater number of writhes when compared to promoted by saline. The venom of P. nattereri has a cytotoxic effect in MDCK and RAW cells and abdominal writhes, which appears to be similar to those caused by acetic acid.

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K-115, a strong and selective inhibitor of Rho-associated coiled coil-forming protein kinase (ROCK), was developed as a therapeutic drug for glaucoma. In long-term phase 3 clinical studies, blepharitis and allergic conjunctivitis were observed. Nonclinical studies were conducted to determine if these adverse effects were caused by the sensitizing potential of K-115. In mouse local lymph node assays (LLNA), sensitizing reactions were not observed at 8.17% w/v of K-115, but weak positive skin sensitivity with a 2.0% K-115 ophthalmic solution was observed. K-115 ophthalmic solution was classified as having slight sensitizing potential. No photosensitization potential was observed with UV-LLNA studies and skin photosensitization studies. In a guinea pig conjunctivitis model study, K-115 had no immediate allergic effect on conjunctivitis, and did not function as an antigen. Furthermore, in ocular toxicity studies in rabbits (26 weeks) and monkeys (52 weeks), no abnormalities were observed in ophthalmic and pathological examinations. Considering the results of nonclinical sensitization and ocular toxicity studies, the clinical adverse effects were possibly not caused by K-115 sensitization potential.

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