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Numerous studies have explored the relationships between exposure to a variety of environmental contaminants, such as polycyclic aromatic hydrocarbons, and induction of cytochrome P450 1A (CYP1A) in different vertebrates. Few controlled studies, however, simulated chronic long-term exposure with repeated non-lethal sampling of the same individuals, which should better represent repeated exposure incidents in animals inhabiting polluted areas. In this study, we investigated the effects of chronic exposure to crude oil on levels of CYP1A1 in endothelial cells of skin biopsies and peripheral mononuclear blood cells in captive river otters (Lontracanadensis) using repeated sampling of the same individuals. We hypothesized that ingestion of oil would result in an increase in levels of CYP1A1 in both targets, and predicted that the relationship between prolonged exposure and expression of CYP1A1 would reach a plateau indicative of continuous detoxification of hydrocarbons. Fifteen wild-caught male otters were acclimated to captivity, and then fed diets containing no oil (control) or diets containing weathered crude oil at 5 mg day(-1) kg(-1) body weight (low-dose) and 50 mg day(-1) kg(-1) body weight (high-dose), at the Alaska Sealife Center in Seward, Alaska, USA. Expression of CYP1A1 was assessed with immunohistochemical analysis of CYP1A1 protein in skin biopsies and by quantitative RT-PCR analysis of CYP1A1 mRNA in mononuclear blood cells. Both assays revealed a decrease between capture and the transfer to captivity, indicating that the enclosure at the Alaska Sealife Center, and the food we offered to the otters were free of potential inducers of CYP1A1. During the exposure period, increases in CYP1A1 expression were registered by both techniques, followed by a decline in CYP1A1 after oil administration ended. Levels of endothelial CYP1A1 in the high-dose group were comparable to those recorded for wild river otters in PWS in 1996 and 1997. Levels of CPY1A1 mRNA in mononuclear blood cells, however, were well below levels recorded for river otters in Prince William Sound, and no correlation was detected between values obtained from the two methods. Thus, our results from this longitudinal study with repeated sampling of the same individuals provide support for the use of cytochrome P450 1A1 as a biomarker for hydrocarbon exposure. Nonetheless, our results also suggest that the induction process of CYP1A1 may be complicated and interacting with other processes in vivo. Such interactions may obscure our ability to describe specific, quantitative, predictable, dose-response relationships between exposure to hydrocarbons and induction of CYP1A1, which are required of reliable biomarkers. Evaluations of such interactions based on theoretical physiological models in live-animals merit further investigation.

The objectives of this study were: (a) to determine the antitumor activity and toxicity of a cyclooxygenase inhibitor (piroxicam) combined with cisplatin chemotherapy in dogs with naturally-occurring, invasive transitional cell carcinoma (TCC) of the urinary bladder; and (b) to determine the effects of this treatment on prostaglandin E(2) concentration, tumor cell proliferation and apoptosis, and angiogenesis. Pet dogs with naturally-occurring invasive TCC underwent complete tumor staging before and after 10 weeks of piroxicam/cisplatin treatment. Prostaglandin E(2) concentrations were determined by immunoassay in snap-frozen tumor tissues. Apoptosis (terminal deoxynucleotidyl transferase-mediated nick end labeling assay), proliferation (proliferating cell nuclear antigen), and microvessel density were determined in formalin-fixed tissues. Urine basic fibroblast growth factor and vascular endothelial cell growth factor concentrations were determined by immunoassay. Partial remission (> or =50% reduction in tumor volume) was noted in 6 of 12 dogs treated with piroxicam/cisplatin. Renal toxicity was dose-limiting. Apoptotic index doubled with treatment in 11 of 12 dogs but was not associated with tumor response. Proliferative index decreased in five dogs, and tumor decreased in size in three of the five dogs. Change in urine basic fibroblast growth factor and vascular endothelial cell growth factor was associated with tumor response. microvessel density was not associated with tumor response. In conclusion, piroxicam/cisplatin had antitumor activity against canine TCC, a disease that closely mimics human invasive urinary bladder cancer. Strategies to prevent renal toxicity of this protocol are needed. Induction of tumor apoptosis and reduction in angiogenic factor concentrations were observed, but additional studies are needed to further define the mechanisms of the antitumor activity of piroxicam/cisplatin.