PCB induced [3H]-labeled ryanodine activation and binding in adult zebrafish skeletal muscle. (A) Depiction of congener structure and relative RYR activation. (B) [³H]-ryanodine (Ry) binding was measured in the presence of specific PCB congeners at 0.1–50 µM. Specific binding shown as a percentage of the DMSO control. Data presented as mean ± SEM from six adult (∼1 year old) zebrafish.

PCB exposures did not significantly decrease viability (congeners listed in order of increasing RYR binding affinity). Larvae were observed for overt malformations or mortalities at 1, 3, 4, and 5 days post-fertilization (dpf). Data are presented as mean percentage (malformed and dead) or mean percentage (viable) ± SEM from ≥3 separate spawns. The total larvae per exposure (Vehicle (Veh), 0.1, 0.3, 1.0, 3.0, and 10 µM) was the following: PCB 66: 32, 60, 61, 63, 60, and 60; PCB 28: 23, 45, 44, 48, 48, and 47; PCB 153: 28, 58, 58, 58, 60, and 60; PCB 138: 28, 59, 61, 63, 59, and 59; PCB 84: 32, 56, 56, 57, 52, and 57; PCB 95: 61, 85, 115, 111, 113, and 119.

PCB exposure (10 µM) significantly alters larval photomotor behavior at 3 and 5 days post-fertilization (dpf) compared to the vehicle (DMSO) control in a RYR-dependent pattern. Examples of photomotor behavior at 3, 4, and 5 dpf from embryos exposed to only vehicle (DMSO, black lines) or 10 µM (grey line) of PCB 66 (low RYR-activity), PCB 153 (mid-level RYR-activity) and PCB 95 (high RYR-activity). The 35-min behavioral testing period was divided into five epochs: 0–5 min = acclimation period, 5–10 min = Light 1, 11–15 = Dark 1, 16–20 min = Light 2 and 21–35 min = Dark 2. Shaded areas correspond to dark periods. Data are presented as mean ± SEM (n = 74, 74, and 55 for PCB 95-exposed embryos and n = 75, 75, and 60 for vehicle control embryos on 3, 4, and 5 dpf, respectively).

PCB levels in pooled whole fish at 5 dpf exposed to PCB starting at 6 hpf. Each point represents the average body burden in ng per pooled sample of 36–51 larvae collected at 5 dpf. Wet weight per pool is approximately 1 mg, allowing for the extrapolation to mg/kg.

Congener rankings. Rankings were assigned to each congener based on the average ranking from three assays: RYR binding, behavior and body burden. (A) Relative congener neurotoxicity in the larval zebrafish with PCB 95 being the most potent. (B) Individual scores for each assay, average ranking and overall ranking.