PON1 and systemic inflammatory response syndrome: Moreover, through a preliminary analysis of samples from dogs with inflammation potentially associated with oxidative stress, we provided evidence that increases of PCOs are evident in dogs in which the activity of the antioxidant enzyme PON-1 is decreased, thus supporting the possible role of PCOs, eventually associated with PON-1, in differentiating dogs with oxidative stress associated with SIRS from those with systemic or localized inflammation in which oxidative stress plays a minor role.