[Metabolism of mitomycin C by human liver microsomes in vitro].

To provide the profiles of metabolism of mitomycin C (MMC) by human liver microsomes in vitro, MMC was incubated with human liver microsomes, then the supernatant component was isolated and detected by HPLC. Types of metabolic enzymes were estimated by the effect of NADPH or dicumarol (DIC) on metabolism of MMC. Standard, reaction, background control (microsomes was inactivated), negative control (no NADPH), and inhibitor group (adding DIC) were assigned, the results were analyzed by Graphpad Prism 4. 0 software. Reaction group compared with background control and negative control groups, 3 NADPH-dependent absorption peaks were additionally isolated by HPLC after MMC were incubated with human liver microsomes. Their retention times were 10. 0, 14. 0, 14. 8 min ( named as Ml, M2, M3) , respectively. Their formation was kept as Sigmoidal dose-response and their Km were 0. 52 (95% CI, 0. 40 - 0.67) mmol x L(-1), 0. 81 (95% CI, 0. 59 - 1. 10) mmol x L(-1), 0. 54 (95% CI, 0. 41 -0. 71) mmol x L(-1) , respectively. The data indicated that the three absorption peaks isolated by HPLC were metabolites of MMC. DIC can inhibit formation of M2, it' s dose-effect fitted to Sigmoidal curve and it' s IC50 was 59. 68 (95% CI, 40. 66 - 87. 61) micromol x L(-1) , which indicated DT-diaphorase could take part in the formation of M2. MMC can be metabolized by human liver microsomes in vitro, and at least three metabolites of MMC could be isolated by HPLC in the experiment, further study showed DT-diaphorase participated in the formation of M2.

A rat model of bone cancer pain induced by intra-tibia inoculation of Walker 256 mammary gland carcinoma cells.

This study described a modified rat model of bone cancer pain. Syngeneic Walker 256 mammary gland carcinoma cells were injected into the tibia medullary cavity via intercondylar eminence. Series of tests were carried out including bone radiology, bone histology, ambulatory pain, thermal hyperalgesia, mechanical allodynia, weight bearing ability, and electrophysiological recording from primary afferent fibers. The rats inoculated with carcinoma cells showed significant ambulatory pain, mechanical allodynia, and reduction in weight bearing, as well as increased incidence of spontaneous activity in Abeta fibers in affected limb, whereas PBS (vehicle) or heat-killed cells (sham) injected rats showed no significant difference in comparison to normal rats. The pain hypersensitive behaviors were aggravated with time and destruction of bone. Interestingly, mechanical allodynia was also observed in the contralateral limb, indicating the involvement of 'mirror image' pain in bone cancer pain. In summary, the present study provided a useful and easily established rat model of bone cancer pain which will contribute to further study of the mechanisms underlying cancer pain.

Effect of in vitro and in vivo treatment with mitomycin C on activities of CYP2D1/2, CYP2C11, and CYP1A2 in rat liver.

AIM: To evaluate the effect of in vitro and in vivo treatment with mitomycin C (MMC) on activities of CYP2D1/2, CYP2C1 , and CYP1A2 in the liver of male rats. METHODS: Using HPLC to determine the activities of the three isoenzymes in rat liver microsomes by detecting the specific metabolites of their substrates after treatment with inducers in vivo or inhibitors in vitro. RESULTS: In vitro, MMC inhibited the activity of CYP2D1/2, CYP2C11, and CYP1A2 in dexamethasone-induced microsomes by (19 +/- 6)% (P < 0.05), (85 +/- 10)% (P < 0.01), and (36 +/- 6)% (P < 0.05), respectively, and decreased the activity of CYP1A2 in beta-naphthoflavone-induced microsomes by (58 +/- 6)% (P < 0.01). Rats were injected intraperitoneally with 20% of the LD50 of MMC for 3 or 6 d. The treatment showed no significant effect on microsomal activities of CYP2D1/2, CYP2C11 or CYP1A2. CONCLUSION: MMC can inhibit the activities of CYP2D1/2, CYP2C11, and CYP1A2 in rat liver microsomes in vitro, but it showed no significant effect on the activities of the three isoenzymes in vivo.