In Vivo Microdialysis Sampling of Phenol and Phenyl Glucuronide in the Blood of Unanesthetized Rainbow Trout: Implications for Toxicokinetic Studies

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In Vivo Microdialysis Sampling of Phenol and Phenyl Glucuronide in the Blood of Unanesthetized Rainbow Trout: Implications for Toxicokinetic Studies. McKim J. M., Jr., McKim, J. M., Sr., Naumann, S., Hammermeister, D. E., Hoffman, A. D., and Klaassen, C. D. (1993). Fundam. Appl. Toxicol., 20, 190-198.Microdialysis (MD) is a sampling method that allows continuous in vivo collection of free, unbound chemicals in blood and interstitial fluids. In the present study we describe a surgical method for placement of a MD probe in the dorsal aorta of 600-to 900-g rainbow trout (Onchorhynchus mykiss). A specially designed probe guide was inserted into the dorsal aorta via the mouth. A PE-50 polyethylene cannula was then inserted into the probe guide and used to further position and maintain the probe guide in the dorsal aorta. Once proper placement of the probe guide was ascertained, the Cannula was removed and a CMA-10 MD probe (4-mm tip) was inserted. The animal was then placed into a respirometer-metabolism chamber and allowed to recover from anesthesia. The placement and functionality of the probe were evaluated by examining the in vivo toxicokinetics of phenol (PH) and phenyl glucuronide (PG) in the blood of an unanesthetized rainbow trout exposed to waterborne PH (7.0 mg/liter). Prior to and following the introduction of PH into the metabolism chamber, MD samples (150 μl) were collected at 30-min intervals and analyzed for free plasma PH and PG by HPLC. Total PH in exposure water and blood was also monitored every 30 min. Free PH and total PH in plasma accumulated rapidly and reached apparent steady-state levels of 54 and 142 pmol/μl, respectively, in about 60 min. A blood;water partition coefficient of 2.0-2.6 was determined from these data, while bound and free plasma PH were 60 and 40%, respectively. PG was not detected until approximately 90 min of PH exposure. After 3 hr, PH exposure was stopped, and MD and water samples were collected during the depuration phase. Free plasma PH decreased rapidly to near pre-exposure levels. In contrast, free PG continued to increase throughout exposure and depuration at a constant rate over a wide range of plasma PH concentrations.