科研之友
微信
新浪微博
Facebook
分享链接
摘要
Six studies were performed regarding the effects of atrazine, the most frequently detected pesticide in fresh water in the US, on developing Xenopus laevis tadpoles exposed 5 days post-hatch through Nieuwkoop Faber Stage 62. The levels of atrazine tested included those potentially found in puddles, vernal ponds and runoff soon after application (200 and 400 mu g/L) and a low level studied by a number of other investigators (25 mu g/L). One study tested 0,25 and 200 mu g/L, another tested 0,200 and 400 mu g/L, while the remaining four studies tested 0 and 400 mu g/L. During all exposures, mortality, growth, metamorphosis, sex ratio, fat body (a lipid storage organ) size and liver weights, both relative to body weight, were evaluated. In selected studies, feeding behavior was recorded, livers and fat bodies were histologically evaluated, liver glycogen and lipid content were determined by image analysis, and immunohistochemical detection of activated caspase-3 in hepatocytes was performed. The NOEC was 25 mu g/L None of these exposure levels changed sex ratios nor were intersex gonads noted, however, no definitive histological evaluation of the gonads was performed. Although a marginal increase in mortality at the 200 mu g/L level was noted, this was not statistically significant. Nor was there an increase in mortality at 400 mu g/L versus controls. At the 400 mu g/L level, tadpoles were smaller than controls by 72 h of exposure and remained smaller throughout the entire exposure. Appetite was not decreased at any exposure level. Slowed metamorphosis was noted only at 400 mu g/L in two of five studies. Livers were significantly smaller in the study that tested both 200 and 400 mu g/L, yet no pathological changes or differences in glycogen or lipid stores were noted. However, livers from 400 mu g/L exposed tadpoles had higher numbers of activated caspase-3 immunopositive cells suggesting increased rates of apoptosis. Fat body size decreased significantly after exposure to 200 and 400 mu g/L although these organs still contained some lipid and lacked any pathology. Since this was noted across all studies, it was considered the most sensitive indicator of atrazine exposure measured. The changes noted in body and organ size at 200 and 400 mu g/L atrazine indicated exposure throughout development compromised the tadpoles. Significant reductions in fat body size could potentially decrease their ability to survive the stresses of metamorphosis or reduce reproductive fitness as frogs rely on stored lipids for these processes.
- 出版日期2011-8
