Absorption dynamics of organic chemical transport across trout gills as related to XXXX -water partition coefficient.

@entity17040 @entity5660 @entity10333 @entity42938
An in vivo fish preparation was used that allowed a direct measure of the transport rates of 14 different organic chemicals across the gills of @entity5660 ( @entity5660 ). The chemicals, all C14 labeled, were selected from five classes, encompassing a range of @entity10333 -water partition coefficient (log P) values, from 0.23 ( @entity42938 ) to 7.5 ( @entity17040 ). The uptake efficiency (extraction efficiency) of each chemical was determined by monitoring the inspired and expired water of trout exposed to each chemical over an exposure period of 1 to 6 hr. The mean gill extraction efficiency for all chemicals tested varied from a low of 7% to a high of 60%, extracted in a single pall of the chemical across the gills. The extraction efficiency of chemicals with log P or 1 or less were low and showed no relationship to log P. These low extraction efficiencies seen at log P of 1 and below with molecular weights below 100 were indicative of aqueous pore transport. The mean extraction efficiency for chemicals with log P values of 1 to 3 seemed to vary directly with log P, to a maximum of slightly greater than 60%, suggesting that uptake was controlled by the lipid membrane. The mean extraction efficiency for chemicals with log P of 3 to 6 was independent of log P and remained at 60%, which suggested that gill uptake was controlled by aqueous diffusion rates rather than gill membrane permeability. The mean extraction efficiency with mirex (log P = 7.5) decreased to 20%. This behavior was consistent with previous physical models which predict that high log P and melting point (low water solubility) may substantially reduce the rate of accumulation in fish. These studies support the passive diffusion model for the uptake of organics at the gill-water interface.
