Serum paraoxonase 1 (PON1) activity in bottlenose dolphins (Tursiops truncates): influence of different substrates and genetic polymorphisms

Background: Paraoxonase-1 (PON1) is an HDL-bound esterase and lipolactonase involved in organophosphate detoxification, protection against oxidative damage. PON1 acts as negative acute phase reactant (APR). Based on the different PON1 functions, several substrates have been identified to evaluate PON1 activities, which are influenced by single-nucleotide polymorphisms (SNPs) such as Leu55Met and Gln192Arg. No data on PON1 activity and SNPs are available for dolphins. Objective: to evaluate the serum PON1 activity using different substrates and SNPs in bottlenose dolphins. Methods: Serum samples from under human-care bottlenose dolphins were used: in 42 healthy animals paraoxonase activity was evaluated using paraoxon as substrate. Arylesterase and lactonase activity were evaluated in samples from 6 healthy and 6 diseased animals using 4-nitrophenyl acetate (4-nPA), phenyl-acetate, and dihydrocoumarin. In 15 animals, PON1 gene was screened for Leu55Met and Gln192Arg SNPs. Results: paraoxonase activity showed mean values of 6.6±4.5 U/mL (median: 7.2 U/mL). Arylesterase activity using 4-nPA was 186.2±20.4 U/L (median: 187.2 U/L) in healthy dolphins and 177.5±14.3 U/L (median: 177.5 U/L) in diseased dolphins, while using phenyl-acetate, PON1 activity had high variability with no reaction or negative results. The lactonase activity was not detectable in any dolphins. All the animals showed homozygosis for Leu55 and Arg192. Conclusions: paraoxonase activity in bottlenose dolphins is lower compared to domestic animals, thus its use as a negative APR is hampered. Arylesterase activity was higher, but without significant differences between healthy and diseased animals. The SNPs seems not to be associated with an elevated paroxonase activity, as reported for humans.