In Vivo and In Vitro Liver and Gill EROD Activity in Rainbow Trout (Oncorhynchus mykiss) Exposed to the Beta-Blocker Propranolol Abigail E. Bartram, 1 Matthew J. Winter, 1 Duane B. Huggett, 2 * Paul McCormack, 1 Lisa A. Constantine, 2 Malcolm J. Hetheridge, 1 Thomas H. Hutchinson, 1 y Lewis B. Kinter, 3 Jon. F. Ericson, 2 John P. Sumpter, 4 Stewart F. Owen 1,4 1 AstraZeneca, Safety Health and Environment, Brixham Environmental Laboratory, Freshwater Quarry, Brixham, Devon, TQ5 8BA, United Kingdom 2 Pfizer Global Research and Development, Groton Laboratories, Eastern Point Road, Groton, Connecticut 06340 3 AstraZeneca Pharmaceuticals US, 1800 Concord Pike, Wilmington, Delaware 19850 4 Institute for the Environment, Brunel University, Uxbridge, Middlesex, UB8 3PH United Kingdom Received 14 June 2010; revised 8 November 2010; accepted 8 November 2010 ABSTRACT: The conservation of common physiological systems across vertebrate classes suggests the potential for certain pharmaceuticals, which have been detected in surface waters, to produce biological effects in nontarget vertebrates such as fish. However, previous studies assessing the effects of such com- pounds in fish have not taken into account the potential for metabolism and elimination. This study aimed to assess if propranolol, a b-adrenergic receptor antagonist or b-blocker, could modulate EROD activity (indica- tive of CYP1A activity) in rainbow trout (Oncorhynchus mykiss) gills and liver. For this, an in vivo time course ex- posure with 1 mg/L was conducted. Additionally, using measured in vivo plasma concentrations, an in vitro ex- posure at human therapeutic levels was undertaken. This allowed comparison of in vitro and in vivo rates of EROD activity, thus investigating the applicability of cell preparations as surrogates for whole animal enzyme activity analysis. In vitro exposure of suspended liver and gill cells at concentrations similar to in vivo levels resulted in EROD activity in both tissues, but with significantly higher rates (up to six times in vivo levels). These results show that propranolol exposure elevated EROD activity in the liver and gill of rainbow trout, and that this is demonstrable both in vivo (albeit nonsignificantly in the liver) and in vitro, thus supporting the use of the latter as a surrogate of the former. These data also provide an insight into the potential role of the gill as a site of metabolism of pharmaceuticals in trout, suggesting that propranolol (and feasibly other pharmaceuticals) may undergo ‘‘first pass’’ metabolism in this organ. # 2011 Wiley Periodicals, Inc. Environ Toxicol 00: 000–000, 2011. Keywords: environmental risk assessment (ERA); xenobiotic metabolism; pharmaceuticals in the environment (PIE); reduction replacement refinement (3Rs); cytochrome (CYP) INTRODUCTION Pharmaceuticals in the environment have attracted increasing interest in the literature (see Fent et al., 2006; Ku ¨mmerer, 2009; Corcoran et al., 2010). Human pharma- ceuticals mainly enter the aquatic environment via the wastewater system (Daughton and Ruhoy, 2009). In most *Department of Biological Sciences, University of North Texas, Denton, TX 76203. y Cefas, Weymouth Laboratory, Barrack Road, The Nothe, Weymouth, Dorset, DT4 8UB. Correspondence to: Stewart Owen; e-mail: stewart.owen@ astrazeneca.com Contract grant sponsor: Pfizer and AstraZeneca (Brunel University) Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/tox.20684  C 2011 Wiley Periodicals, Inc. 1