Department of Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A 1S6, Canada.
Fish Physiol Biochem. 2021 Apr;47(2):265-279. doi: 10.1007/s10695-020-00911-8. Epub 2021 Jan 6.
Biological organisms are constantly challenged by xenobiotics and have evolved mechanisms to reduce, neutralize, or repair toxic outcomes. The various chemical defenses all utilize energy, but their specific costs and impacts on energy budgets are currently unknown. In this study, the energetic costs associated with the induction and substrate transport of the efflux transporter P-glycoprotein (P-gp [ABCB1, MDR1]) were examined in rainbow trout. An intraperitoneal injection of the P-gp inducer clotrimazole (0, 0.1, 1.0, and 10 mg/kg) increased P-gp activity (as measured by a competitive rhodamine 123 transport assay in hepatocytes) in a dose-dependent manner reaching a maximum induction of 2.8-fold. Maximum P-gp induction occurred at 50 h post-administration with the highest dose; significant induction of P-gp activity remained elevated over constitutive values until the last sampling time point (168 h). In vitro measurements of hepatocyte respiration indicated that basal P-gp activity transporting R123 as a substrate did not significantly increase respiration rates (range 18.0 to 23.2 ng O/min/10 cells); however, following the induction of P-gp by clotrimazole and exposure to the P-gp substrate R123, respiration rates increased significantly (3.52-fold) over baseline values. Using whole animal respirometry, it was shown that respiration rates in fish exposed to R123 only or induced with clotrimazole were not different from controls (range 1.2 to 2.1 mg O/kg/min); however, respiration rates were significantly increased in fish with induced P-gp levels and also exposed to R123. This work indicates that basal and induced levels of P-gp activity do not incur significant energetic costs to fish; however, upon induction of P-gp and concomitant substrate exposures, energetic costs can increase and could pose challenges to organisms facing limited energy resources.
生物机体不断受到外源性化学物质的挑战，因此进化出了多种减少、中和或修复毒性作用的机制。各种化学防御机制都需要消耗能量，但它们的具体成本和对能量预算的影响目前尚不清楚。在这项研究中，我们研究了虹鳟鱼中 P 糖蛋白（P-gp [ABCB1, MDR1]）外排转运体的诱导和底物转运相关的能量成本。腹腔内注射 P-gp 诱导剂克霉唑（0、0.1、1.0 和 10mg/kg）可剂量依赖性地增加 P-gp 活性（通过肝细胞中竞争性罗丹明 123 转运测定法测量），最大诱导倍数为 2.8 倍。最高剂量给药后 50 小时达到最大 P-gp 诱导，P-gp 活性的显著诱导持续高于基础值，直到最后一个采样时间点（168 小时）。肝细胞呼吸的体外测量表明，作为底物转运的基础 P-gp 活性不会显著增加呼吸速率（范围 18.0 至 23.2ng O/min/10 个细胞）；然而，在克霉唑诱导 P-gp 并暴露于 P-gp 底物 R123 后，呼吸速率显著高于基础值（增加 3.52 倍）。使用整体动物呼吸测量法，结果表明，仅暴露于 R123 或用克霉唑诱导的鱼的呼吸速率与对照组无差异（范围 1.2 至 2.1mg O/kg/min）；然而，在诱导 P-gp 水平并同时暴露于 R123 的鱼中，呼吸速率显著增加。这项工作表明，基础和诱导的 P-gp 活性水平不会给鱼类带来显著的能量成本；然而，在诱导 P-gp 并同时暴露于底物时，能量成本可能会增加，并可能对面临有限能量资源的生物体构成挑战。
