Oxidative stress biomarkers and heart function in bullfrog tadpoles exposed to Roundup Original (R)

Oxidative stress biomarkers, in vivo heart rate (f(H)), and contraction dynamics of ventricle strips of bullfrog (Lithobates catesbeiana) tadpoles were evaluated after 48 h of exposure to a sub-lethal concentration (1 ppm) of the herbicide Roundup Original (R) (glyphosate 41%). The activities of the antioxidant enzymes superoxide dismutase and catalase were increased in the liver and decreased in muscle, while oxidative damage to lipids increased above control values in both tissues, showing that the generation of reactive oxygen species and oxidative stress are involved in the toxicity induced by Roundup (R). Additionally, tadpoles' hyperactivity was associated with tachycardia in vivo, probably due to a stress-induced adrenergic stimulation. Ventricle strips of Roundup (R)-exposed tadpoles (R-group) presented a faster relaxation and also a higher cardiac pumping capacity at the in vivo contraction frequency, indicating that bullfrog tadpoles were able to perform cardiac mechanistic adjustments to face Roundup (R)-exposure. However, the lower maximal in vitro contraction frequency of the R-group could limit its in vivo cardiac performance, when the adrenergic-stimulation is present. The association between the high energetic cost to counteract the harmful effects of this herbicide and the induction of oxidative stress suggest that low and realistic concentrations of Roundup (R) can have an impact on tadpoles' performance and success, jeopardizing their survival and/or population establishment.17315316

The liver monooxygenase system of Brazilian freshwater fish

Content of cytochromes b(5) and P-450, and activities of NADPH-cytochrome c (P-450) reductase (NCR) and 7-ethoxyresorufin O-deethylase (EROD) were measured in liver microsomes prepared from two South American endemic fish, Brycon cephalus and Colossoma macropomum, from tilapia, Oreochromis niloticus, and from Swiss mice, Mus musculus. which served as a control. Strong hemoglobin binding to fish liver microsomal membranes (FLM) altered visible spectra of microsomal cytochromes. Consequently, special precautions during FLM preparation, including liver perfusion followed by repeated washing of microsomes, were required in the study of microsomal cytochromes from these fish. FLM from all fish studied here had a significantly lower content of microsomal cytochromes but a similar level of NCR and EROD activities compared to mouse liver microsomes (MLM). Strong response of the monooxygenase system in O. niloticus to water pollution was detected with both specific cytochrome P-450 content and EROD activity increasing sharply. The optical spectra of hemoglobin from B. cephalus and C. macropomum were analyzed and some differences in shape and relative extinction were observed compared to known hemoglobins. (C) 2000 Elsevier Science Inc. All lights reserved.1261293