Rubber additives induce oxidative stress in rainbow trout

Area of Science:

• Environmental toxicology
• Aquatic ecotoxicology
• Fish physiology

Background:

• Rubber leachate, particularly from tires, is known to be toxic to aquatic organisms.
• Rubber additives and their metabolites can enter aquatic environments.

Purpose of the Study:

• To investigate the effects of rubber leachate from a hose on rainbow trout (Oncorhynchus mykiss).
• To identify rubber chemicals and their metabolites in exposed fish.
• To assess the impact of specific rubber additives (MBT and DPA) on fish liver biochemistry.

Main Methods:

• Exposure of rainbow trout to water from a rubber hose.
• Chemical analysis of water samples for rubber additives and related compounds.
• Analysis of fish bile for parent compounds and metabolites.
• Injection of rainbow trout with 2-mercaptobenzothiazole (MBT) and diphenylamine (DPA) to study biochemical effects.
• Measurement of hepatic enzyme activities (EROD, GR, GST) and glutathione concentrations.

Main Results:

• Increased hepatic ethoxyresorufin-O-deethylase (EROD) and glutathione reductase (GR) activity in fish exposed to rubber hose water.
• Identification of 2-mercaptobenzothiazole (MBT), diphenylamine (DPA), and hydroxylated polycyclic aromatic hydrocarbons in water and fish bile.
• Detection of parent compounds and metabolites in fish bile.
• MBT and DPA injections altered total glutathione (tGSH) levels.
• MBT injection increased hepatic GR and glutathione S-transferase (GST) activity.
• Hydroxylated DPA was the primary metabolite in DPA-injected fish bile.

Conclusions:

• Rubber chemicals can leach from hoses into aquatic environments.
• Rainbow trout can uptake and metabolize these leached rubber chemicals.
• Exposure to rubber additives like MBT and DPA can induce biochemical changes in fish, including the up-regulation of antioxidant defense systems.