The objective of this study was to compare the plasma protein binding rates (PPBRs) of doxycycline (DC) in the plasma of grass carp (Ctenopharyngodon idella), yellow catfish (Pelteobagrus fulvidraco) and crayfish (Procambarus clarkii) at different temperatures (4, 18 and 25celcius) with different concentrations (1, 5, 10 and 20 mu g/ml). A rapid and simple method of ultrafiltration (UF) was employed to determine the PPBR of DC in the plasma. The results showed that PPBRs were increased with the rise of the concentration of DC at the same temperature. At 4 celcius, PPBRs were increased from 90.00% to 99.51%, 89.81% to 98.71% and 84.08% to 99.21% in the plasma of grass carp, yellow catfish and crayfish respectively. At 18celcius and 25celcius, the same trend was also presented in the three species. Meanwhile, PPBRs of DC might have the atypical nonlinear phenomenon. Otherwise, the temperature could affect the PPBR of DC at a certain degree in the plasma of grass carp and yellow catfish at the same concentration of DC. However, no regularity was presented in the plasma of crayfish. Overall, the increased concentration of DC significantly affected the PPBR in the plasma of grass carp, yellow catfish and crayfish at the same temperature, but the temperature only had a certain influence on the PPBR of grass carp and yellow catfish. Hence, this study is beneficial to design suitable therapeutic regimens and formulations of DC in grass carp, yellow catfish and crayfish at different temperatures.
