The regulation of endogenous metabolites is still not fully understood in aquatic invertebrates exposed concurrently to toxicants and
hypoxia. Despite the prevalence of
hypoxia in the aquatic environment, toxicity estimations seldom account for multiple stressors thereby differing from natural conditions. In this study, we examined the influence of
hypoxia (<30% O2) on contaminant uptake and the composition of intracellular metabolites in Lumbriculus variegatus exposed to
benzo(a)pyrene (B(a)P, 3μgL(-1)),
chlorpyrifos (CPF, 100μgL(-1)) or
pentachlorophenol (PCP, 100μgL(-1)).
Tissue extracts of worms were analyzed for 123 metabolites by gas chromatography-mass spectrometry and metabolite levels were then related to treatments and exposure time.
Hypoxia markedly increased the accumulation of B(a)P and CPF, which underlines the significance of
oxygen in chemical uptake. The
oxygen effect on PCP uptake was less pronounced.
Succinate and glycerol-3-phosphate increased significantly (p<0.0001) following hypoxic treatment, whereas
sugars,
cysteine, and
cholesterol were effectively repressed. The buildup of
succinate coupled with the corresponding decline in intracellular 2-oxo- and 2-hydroxy
glutaric acid is indicative of an active
hypoxia inducible factor mechanism.
Glutamate, and TCA cycle intermediates (
fumarate, and
malate) were disturbed and evident in their marked suppression in worms exposed concurrently to
hypoxia and PCP. Clearly,
hypoxia was the dominant stressor for individuals exposed to B(a)P or CPF, but to a lesser extent upon PCP treatment. And since
oxygen deprivation promotes the accumulation of different toxicants, there may be consequences on species composition of metabolites in natural conditions.