Comparison of the acute effects of benzo-a-pyrene on adult zebrafish (Danio rerio) cardiorespiratory function following intraperitoneal injection versus aqueous exposure

• Published in: Aquatic toxicology Vol. 165; pp. 19 - 30
• Main Authors: Gerger, Courtney J., Weber, Lynn P.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.08.2015
• Subjects: Acute toxicity; Animals; Benzo(a)pyrene - toxicity; Benzo-a-pyrene; Cardiac toxicity; Danio rerio; Environmental Exposure; Exposure route; Injections, Intraperitoneal; Liver - drug effects; Metabolic rate; Polycyclic Aromatic Hydrocarbons - toxicity; Swimming; Water Pollutants, Chemical - toxicity; Zebrafish; Zebrafish - physiology; Metabolic rate; AMR; COT; Zebrafish; I.p; AhR; Cardiac toxicity; BaP; MO2; CYP1A; Ucrit; Benzo-a-pyrene; PAH; SMR; F-AS; Exposure route; Acute toxicity
• ISSN: 0166-445X; 1879-1514
• DOI: 10.1016/j.aquatox.2015.05.008

•Acute benzo-a-pyrene increased oxygen demand and decreased aerobic scope in adult zebrafish.•Despite increased oxygen demand, exposed zebrafish had decreased cardiac output.•Benzo-a-pyrene decreased ventricular rate due to atrioventricular conduction blockade.•Aqueous benzo-a-pyrene had greater cardiorespiratory toxicity than intraperitoneal injection. Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental contaminants. PAH exposure causes developmental toxicity in multiple fish species, while acute adult fish toxicity is thought to be minimal. The literature increasingly suggests sublethal PAH effects may occur, but differences in exposure route may confound conclusions. We hypothesized that acute PAH exposure in adult fish will cause cardiorespiratory impairment that will not differ with exposure route. In order to investigate this hypothesis, adult zebrafish (Danio rerio) were injected intraperitoneal (i.p.) twice with increasing concentrations of the prototypical PAH, benzo-a-pyrene (BaP; 0.1, 10, and 1000μg/kg) or exposed aqueously (static, renewal at 24h; 16.2 and 162μg/L) for 48h and compared to corresponding dimethylsulfoxide controls. No mortalities or significant effects on weight of the fish were noted at any exposure concentration or route. At 48h, fish were subjected to swimming tests with concurrent oxygen consumption measurement (n=10 fish/treatment) or echocardiography (n=12 fish/treatment). Oxygen consumption (MO2) was increased at three swimming speeds in BaP-injected groups compared to control (p<0.01 in Fisher’s LSD tests after two-way ANOVA). In contrast, aqueously BaP-exposed fish showed increased MO2 under only basal conditions. Despite increased oxygen demand, ventricular heart rate was significantly decreased in BaP-exposed fish, both injected and aqueously-exposed. Analysis of BaP body burdens in fish tissue allowed for identification of an overlapping dose group between exposure routes, through which comparisons of cardiorespiratory toxicity were then made. This comparison revealed most effects were similar between the two exposures routes, although minor differences were noted. At similar BaP body burdens, injected fish suffered from more severe bradycardia than aqueously exposed fish and had greater levels of increases in cytochrome P4501A (CYP1A) mRNA levels in liver and heart tissue compared to aqueous exposed fish. In conclusion, acute BaP exposure in adult zebrafish had negative effects on cardiorespiratory function. Differences in effect between exposure routes were attributed primarily to differences in bioavailability, since overall, similar effects were noted between the two exposure routes when similar BaP body burdens were achieved.